Ultrafast Carrier Capture and Auger ... - ACS Publications

Subscriber access provided by University of Otago Library

Letter

Ultrafast Carrier Capture and Auger Recombination in Single GaN/InGaN Multiple Quantum Well Nanowires Stephane Boubanga-Tombet, Jeremy B. Wright, Ping Lu, Michael R.C. Williams, Changyi Li, George T Wang, and Rohit P. Prasankumar ACS Photonics, Just Accepted Manuscript • DOI: 10.1021/acsphotonics.6b00622 • Publication Date (Web): 04 Nov 2016 Downloaded from http://pubs.acs.org on November 5, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Photonics is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

Ultrafast Carrier Capture and Auger Recombination in Single GaN/InGaN Multiple Quantum Well Nanowires Stephane Boubanga-Tombet,∗,† Jeremy B. Wright,‡ Ping Lu,‡ Michael R. C. Williams,† Changyi Li,‡ George T. Wang,‡ and Rohit P. Prasankumar∗,† †Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA ‡Sandia National Laboratories, P.O. Box 5800, MS-1086, Albuquerque, New Mexico 87185, USA E-mail: [email protected]; [email protected]

Abstract Ultrafast optical microscopy is an important tool for examining fundamental phenomena in semiconductor nanowires with high temporal and spatial resolution. Here, we used this technique to study carrier dynamics in single GaN/InGaN core-shell nonpolar multiple quantum well nanowires. We find that intraband carrier-carrier scattering is the main channel governing carrier capture, while subsequent carrier relaxation is dominated by three-carrier Auger recombination at higher densities and bimolecular recombination at lower densities. The Auger constants in these nanowires are approximately two orders of magnitude lower than in planar InGaN multiple quantum wells, highlighting their potential for future light emitting devices.

1 ACS Paragon Plus Environment

ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Keywords GaN/InGaN nanowires, ultrafast optical microscopy, Auger recombination, carrier capture

Group III-nitride (III-N) semiconductors are widely used in commercial optoelectronic devices to efficiently produce light, making them very attractive materials for solid-state lighting 1 . However, traditional light-emitting diodes (LEDs) with planar InGaN quantum wells (QWs) grown on the polar (0001) c-plane possess large internal electric fields that induce the quantum confined Stark effect (QCSE). This spatially separates the electron and hole wave functions, reducing radiative recombination 2,3 . An attractive approach for overcoming this is based on III-N semiconductor nanowires (NWs), which can be synthesized with higher structural quality than conventional heteroepitaxial planar films 4,5 . These NWs are therefore promising unconventional platforms for the growth of nonpolar QWs with low dislocation densities 6 . When NW arrays are selectively grown on 7–9 or etched from 10,11 c-plane GaN on sapphire or (111) silicon, without the use of metal catalysts, the NW axis is along the polar c-direction, but the exposed side-facets are nonpolar (10-10) m-planes. NW heterostructures consisting of GaN cores covered by m-plane InGaN shells can then be grown with minimal polarization effects, potentially increasing radiative recombination. Light emission can be further enhanced by growing InGaN/GaN multiple quantum well (MQW) heterostructures on GaN NWs, which increases internal quantum efficiencies and enables the emission wavelength to be tuned. These nonpolar MQW NW heterostructures thus make it possible to control ultraviolet and visible light emission, leading to novel LEDs 7,12–16 , photovoltaic devices 11 , and nanoscale lasers 17,18 . The implementation and optimization of these GaN/InGaN NW heterostructure-based devices will require a detailed understanding of their physical properties. In particular, by studying the mechanisms governing dynamic processes in these nanosystems, such as carrier capture, relaxation, transport, and recombination, one can shed light not only on


Page 2 of 20

Page 3 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

the timescales on which these processes occur, but also on fundamental parameters such as the diffusion coefficient and surface recombination velocity. 19,20 . These studies must be done on single NWs, since although most applications will employ NW ensembles, the diameter, length, and shape fluctuations between different NWs make it difficult to uncover their intrinsic properties in ensemble measurements 21,22 . While some studies have been carried out on planar InGaN heterostructures 23,24 and multiple quantum wells (MQWs) 25–29 , as well as III-N based NW ensembles 30–34 , to date there has been only one study of ultrafast carrier dynamics in single III-nitride NWs 35 , and none on individual III-N NW core-shell heterostructures, to the best of our knowledge. This can be done using ultrafast optical microscopy (UOM), which has previously been used to reveal the fundamental properties (both static and dynamic) of single NWs and NW heterostructures 36,37 , as well as other nanomaterials 38,39 . Here, we used UOM to study carrier dynamics in single GaN and GaN/InGaN nonpolar MQW core-shell NWs. We find that the timescale for initial carrier relaxation into the quantum wells strongly depends on the photoexcitation fluence, indicating that intraband Auger carrier-carrier scattering may govern carrier capture. The relaxation dynamics are also density dependent; three-carrier Auger recombination dominates the dynamics at high densities, while at lower densities bimolecular recombination is shown to be the main channel governing carrier relaxation. Our results thus shed new light on carrier dynamics in III-N MQW NW heterostructures, particularly by revealing the processes governing carrier capture and relaxation, which should impact future applications of these unique nanosystems. Ultrafast optical microscopy measurements were performed using a experimental setup based on a 100 kHz regeneratively amplified laser producing 50 fs, 10 µJ pulses at 800 nm (1.55 eV) 30,35 ; third harmonic and second harmonic generation were used to generate the pump and probe beams, respectively. We also performed micro-photoluminescence (PL) measurements on single NWs using a separate system. More detail on these experimental setups is given in the supporting information.


ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The core GaN nanowires were fabricated using a top-down approach 11,40,41 followed by the growth of a five-period undoped GaN/In0.08 Ga0.92 N multiple quantum well. Another sample was also fabricated, in which a ∼15 nm thick In0.02 Ga0.98 N underlayer was radially grown on the NW core prior to the MQW growth; this has been previously shown to increase cathodoluminescence yield from GaN/InGaN quantum wells 42 . For optical measurements, the NWs were dry transferred onto a sapphire substrate, enabling the characterization of isolated single NWs. More fabrication details are given in the supporting information.

Figure 1: (a) SEM image of a GaN/InGaN core-shell NW transferred onto sapphire. (b) Schematic illustrating the 3D geometry of the nanowire, as well as a magnified cross-sectional view of the nanowire facet highlighting the InGaN/GaN MQW structure.(c) STEM image of a cross-sectioned nanowire near the tip, showing the m-plane InGaN/GaN MQW structure. (d) Normalized, time-integrated PL spectra of the three NWs examined here. The dotted lines show the 400 and 450 nm probe wavelengths used in the ultrafast optical measurements. Figure 1(a) shows a scanning electron microscope (SEM) image of a representative GaN/InGaN core-shell nanowire (without an InGaN underlayer) with a diameter of ∼320 nm and length of ∼5 µm. The tapered tip is a result of six-fold semipolar {10-11} facets that grow in during the regrowth of the MQW structure 11,43 . Figure 1(b) shows a schematic depicting the 3D structure of the GaN/InGaN core-shell NW. In order to determine the detailed structure, a NW was cross-sectioned using a focused ion beam along the axis for imaging via high-angle annular dark-field aberration-corrected cross-sectional scanning transmission electron microscopy (STEM-HAADF). Figure 1(c) shows a STEM image near the tip of a cross-sectioned nanowire, revealing the GaN/InGaN MQW structure. The m-plane InGaN QW and GaN barrier thicknesses are ∼4.5-5.5 nm and 3 nm, respectively. STEM energy4 ACS Paragon Plus Environment

Page 4 of 20

Page 5 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

dispersive x-ray spectroscopy (STEM-EDS) analysis of the nonpolar InGaN QWs near the tip estimates the In concentration to be ∼7-9% (91-93% Ga). For the semipolar QWs at the tip, the InGaN QW and GaN barrier thicknesses are ∼1.5-3.0 nm and ∼0.7-1.5 nm, respectively, with estimated In concentration ∼10-15%. We note that the average length of the section containing the semipolar QWs at the tip is ∼40 nm, which is less than 1% of the length of the remainder of the NW, containing the nonpolar QWs. Any contribution to the pump-probe signal from the semipolar QWs is thus expected to be negligible. We examined three single NWs: a GaN core-only NW, a GaN core + GaN/InGaN MQW shell NW (Fig. 1(a)) and a GaN core+ GaN/InGaN MQW shell NW with an InGaN underlayer. Figure 1(d) shows the PL spectra of the NWs measured at 300 K, revealing peaks around λ ≈ 364 nm and 405 nm (in GaN core-only and MQW-based NWs, respectively) that indicate the energetic positions of the GaN core and InGaN MQW ground states. We first studied carrier dynamics in the single GaN core-only NW for comparison to the subsequent measurements on GaN/InGaN MQW NWs. Our results, described in the supporting information, are consistent with previous work on ultrafast carrier dynamics in both single and ensemble bottom-up grown GaN NWs 30,31,35,44,45 , revealing fluence-dependent relaxation dominated by mid-gap defect states. We then performed UOM measurements on single GaN/InGaN MQW-based NWs, where relaxation through QW states should dominate carrier dynamics. We begin by noting that throughout all of our experiments, the data from the GaN/InGaN and GaN/InGaN/underlayer NWs were quite similar, except for a small increase in the amplitude of the photoinduced change in transmission (∆T/T) signal and the decay time constants for the NW with the underlayer. This suggests that the InGaN underlayer may reduce non-radiative recombination and increase light emission, consistent with previous work 42,46 . Here, we will primarily focus on carrier dynamics in the GaN/InGaN MQW NW (henceforth referred to as the MQW NW). The 266 nm pump primarily excites carriers into the GaN barriers, with a small fraction photoexcited directly in the GaN cores since the penetration depth in our GaN/InGaN NW


ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

is ∼38 nm (estimated using the complex index of refraction model in Ref. 47), slightly larger than the thickness of the MQW structure. Tuning the probe wavelength allows us to track carriers as they lose energy and relax from the GaN barriers into the MQWs (see Fig. S1 for a simple schematic depicting these excitation and relaxation processes). Figure 2(a) depicts fluence-dependent differential transmission data on the single MQW NW at a probe wavelength of 400 nm (which probes the QW ground state (Fig. 1(d)), revealing a relatively long rise (τr ) followed by two decay processes (τ1 and τ2 ) that were extracted using exponential fits to the data. The inset of this figure shows that τr decreases with increasing pump fluence for F >100 µJ/cm2 (corresponding to photoexcited carrier densities of n >1.74× 1012 cm−2 ). Comparison to Fig. S2 in the supporting information also reveals that the initial stages of carrier relaxation in the GaN/InGaN core/shell NWs differ significantly from that in the single GaN core-only NW (in which the ∼500 fs rise time did not depend on pump fluence). In fact, τr is up to seven times longer in the GaN/InGaN NWs than in the GaN NW. This shows that as expected, different states are being probed at 400 nm in the MQW-based NWs (QW states) and the GaN core-only NW (defect states), further supported by the strong PL signal from the QW states in the GaN/InGaN NWs (Figure 1(d)). In contrast, at 550 nm τr ∼500 fs in all NWs, indicating that some fraction of the photoexcited carriers directly relax from the GaN layers into the YL defect states, regardless of the presence of MQWs. Finally, the decrease in τr with pump fluence enables us to identify density-dependent effects, such as Auger carrier-carrier scattering, as the most likely channel governing intraband carrier relaxation in the single MQW NW. Phonon-mediated processes could also play a role at lower fluences (F ∼2.5x1012 cm−2 per quantum well), while lower fluence data (corresponding to n ≤1.74x1012 cm−2 ) deviates from this dependence. This enabled us to extract values for the third-order Auger constant of C3 ∼ 6.15 × 10−33 cm6 /s, which varied by only ∼ 3% from n =2.5-4.98x1012 cm−2 . We note that the bimolecular recombination model did not fit this data as well (Fig. 3(b), upper panel), yielding values of C2 that varied by a factor of ∼9 over this 8 ACS Paragon Plus Environment

Page 9 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

Figure 3: Time-dependent carrier density extracted from Fig. 2(a) and scaled to (a) [n(0)/n(t)]2 -1) for the three-carrier Auger model and (b) [n(0)/n(t)]-1) for the bimolecular recombination model, for both high (upper panels) and low (lower panels) carrier densities. The carrier densities in the upper panels correspond to fluences of F ≥150 µJ/cm2 , while the lower panels depict F ≤105 µJ/cm2 . Good agreement is obtained (solid lines) when the correct model is used. fluence range and differed by approximately 2 orders of magnitude from previously published results 57,58 . It is also worth mentioning that fits to the data on the MQW NW with an InGaN underlayer yielded a C3 that was 6 times lower, supporting the idea that the underlayer reduces non-radiative recombination 42,46 . Those values are approximately two orders of magnitude smaller than those measured in c-plane planar InGaN/GaN QW laser structures (C3 ∼2×10−31 cm6 /s) 59 while agreeing relatively well with values measured in axial InGaN/GaN dot-in-nanowire samples (C3 ∼4.1×10−33 cm6 /s) 60 , suggesting that LEDs based on these NWs should suffer less from the well-known effect of efficiency droop 32,60 . In contrast, our data at lower fluences agrees much better with the bimolecular recombination model (Fig. 3(b)), yielding second-order Auger constants of C2 ∼2.01× 10−11 cm3 /s that varied by only ∼ 7% from n =0.72-1.74x1012 cm−2 . This also agrees well with previous results (C2 ∼2×10−11 cm3 /s) 57 and (C2 ∼1×10−11 cm3 /s) 58 . We note that TRPL measurements on similar GaN/InGaN MQW NWs with fluences up to ∼130 µJ/cm2 revealed that three-carrier Auger recombination was suppressed 32 ; our results indicate that bimolecular recombination may instead have been the dominant relaxation mechanism in their NWs.


ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Finally, we observed that the NW with an underlayer also yielded a C2 about 2.5 times lower than that for the MQW NW. To get more physical insight into this, we note that exciton formation is possible only for carrier densities lower than the Mott density, NM ∼ 1/πadB 61 , where d is the system dimensionality (d=2 for quantum wells) and aB is the exciton Bohr radius. For the MQW NWs studied here, with aB ∼3.5 nm 61 , NM ∼2.6 x 1012 cm−2 . At low excitation densities (n < NM ), excitons are thus created within the MQW layers of our GaN/InGaN core/shell NWs (unlike in the GaN core-only NW, which is too large for exciton formation), after which they undergo bimolecular recombination. As the photoexcited carrier density n increases beyond NM , the exciton binding energy is reduced due to carrier screening, preventing exciton formation; in this regime three-carrier Auger recombination therefore dominates the observed dynamics. This agrees well with our data, which shows a transition from bimolecular to Auger recombination around n ∼2 x 1012 cm−2 , comparable to NM . In general, our results are consistent with previous work on Auger recombination in semiconductor NWs 22,48,54,62 . In conclusion, we have investigated intraband and interband carrier dynamics in single top-down fabricated GaN and GaN/InGaN core-shell nonpolar MQW nanowires using ultrafast optical microscopy, shedding light on the physical mechanisms that directly influence light emission from III-N nanowire heterostructures. We find that unlike in single GaN core-only NWs, where carrier relaxation is primarily governed by midgap defect states, the dynamics in GaN/InGaN MQW NWs are dominated by the QW states. In particular, carrier capture into the MQWs occurs on a timescale of a few picoseconds and is likely governed by carrier-carrier scattering. Subsequent carrier relaxation is governed primarily by threecarrier Auger recombination at high excitation densities and bimolecular recombination at low densities, with Auger constants two orders of magnitude lower than those reported for planar InGaN MQWs. Our results have several implications for the future development of III-N NW-based solidstate lighting devices, as τr determines how fast electrons populate the QWs after electronic


Page 10 of 20

Page 11 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

or optical injection and τ2 governs how rapidly these devices can be modulated, as well as how long carriers can sustain population inversion. Our results imply that non-radiative Auger recombination is primarily responsible for efficiency droop in III-nitride NWs; 60,63–65 however, the low Auger constants also suggest that optimizing the design of these top-down fabricated MQW NWs may make them more viable for applications. These results thus demonstrate that ultrafast optical microscopy can provide important insight into parameters critical for future applications of III-N NW-based optoelectronic devices.

Acknowledgement We thank Igal Brener and Sheng Liu for help with PL measurements and Dmitry Turchinovich for helpful discussions. This work was supported by the Department of Energy, Office of Basic Energy Sciences, Division of Materials Science, and performed in part at the Center for Integrated Nanotechnologies (CINT), a U.S. Department of Energy, Office of Basic Energy Sciences (BES) user facility, under user proposal U2014B0089. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is operated by Los Alamos National Security, LLC, for the National Nuclear Security administration of the U.S. Department of Energy under contract no. DE-AC52-06NA25396. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy National Nuclear Security Administration under contract no. DE-AC04-94Al85000.

Supporting Information Available The following files are available free of charge. Supporting Information for the description of the experimental setup and sample fabrications as well as ultrafast optical microscopy on the single GaN core-only NW.


ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

References (1) Nakamura, S.; Pearton, S.; Fasol, G. The Blue Laser Diode: The Complete Story; Springer-Verlag: Berlin, 2000. (2) Masui, H.; Nakamura, S.; DenBaars, S. P.; Mishra, U. K. Nonpolar and Semipolar IIINitride Light-Emitting Diodes: Achievements and Challenges. IEEE Transactions on Electron Devices 2010, 57, 88–100. (3) Shen, H.; Wraback, M.; Zhong, H.; Tyagi, A.; DenBaars, S.; Nakamura, S.; Speck, J. Unambiguous evidence of the existence of polarization field crossover in a semipolar InGaN/GaN single quantum well. Appl. Phys. Lett. 2009, 95, 3503. (4) Wang, C.-Y.; Chen, L.-Y.; Chen, C.-P.; Cheng, Y.-W.; Ke, M.-Y.; Hsieh, M.-Y.; Wu, H.M.; Peng, L.-H.; Huang, J. GaN nanorod light emitting diode arrays with a nearly constant electroluminescent peak wavelength. Opt. Express 2008, 16, 10549–10556. (5) Nguyen, H. P. T.; Zhang, S.; Cui, K.; Han, X.; Fathololoumi, S.; Couillard, M.; Botton, G. A.; Mi, Z. p-Type Modulation Doped InGaN/GaN Dot-in-a-Wire White-LightEmitting Diodes Monolithically Grown on Si(111). Nano Lett. 2011, 11, 1919–1924. (6) Li, Q.; Wang, G. T. Strain influenced indium composition distribution in GaN/InGaN core-shell nanowires. Appl. Phys. Lett. 2010, 97, 181107. (7) Hong, Y. J.; Lee, C.-H.; Yoon, A.; Kim, M.; Seong, H.-K.; Chung, H. J.; Sone, C.; Park, Y. J.; Yi, G.-C. Visible-Color-Tunable Light-Emitting Diodes. Adv. Mater. 2011, 23, 3284–3288. (8) Yeh, T.-W.; Lin, Y.-T.; Stewart, L. S.; Dapkus, P. D.; Sarkissian, R.; O’Brien, J. D.; Ahn, B.; Nutt, S. R. InGaN/GaN multiple quantum wells grown on nonpolar facets of vertical GaN nanorod arrays. Nano Lett. 2012, 12, 3257–3262.


Page 12 of 20

Page 13 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

(9) Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.; Calleja, E.; Jahn, U. Selective area growth and characterization of InGaN nanocolumns for phosphor-free white light emission. Journal of Applied Physics 2013, 113, 114306. (10) Chang, J.-R.; Chang, S.-P.; Li, Y.-J.; Cheng, Y.-J.; Sou, K.-P.; Huang, J.-K.; Kuo, H.C.; Chang, C.-Y. Fabrication and luminescent properties of core-shell InGaN/GaN multiple quantum wells on GaN nanopillars. Appl. Phys. Lett. 2012, 100, 261103. (11) Wierer Jr, J. J.; Li, Q.; Koleske, D. D.; Lee, S. R.; Wang, G. T. III-nitride core-shell nanowire arrayed solar cells. Nanotechnology 2012, 23, 194007. (12) Wang, G. T.; Li, Q.; Wierer, J. J.; Koleske, D. D.; Figiel, J. J. Top-down fabrication and characterization of axial and radial III-nitride nanowire LEDs. Phys. Status Solidi A 2014, 211, 784–751. (13) Koester, R.; Sager, D.; Quitsch, W. A.; Pfingsten, O.; Poloczek, A.; Blumenthal, S.; Keller, G.; Prost, W.; Bacher, G.; Tegude, F. J. High-Speed GaN/GaInN Nanowire Array Light-Emitting Diode on Silicon(111). Nano Lett. 2015, 15, 2318–2323. (14) Ra, Y.-H.; Navamathavan, R.; Yoo, H.-I.; Lee, C.-R. Single nanowire light-emitting diodes using uniaxial and coaxial InGaN/GaN multiple quantum wells synthesized by metalorganic chemical vapor deposition. Nano Lett. 2014, 14, 1537–1545. (15) Li, S.; Waag, A. GaN based nanorods for solid state lighting. Journal of Applied Physics 2012, 111, 071101. (16) Koester, R.; Sager, D.; Quitsch, W.-A.; Pfingsten, O.; Poloczek, A.; Blumenthal, S.; Keller, G.; Prost, W.; Bacher, G.; Tegude, F.-J. High-speed GaN/GaInN nanowire array light-emitting diode on silicon (111). Nano Lett. 2015, 15, 2318–2323. (17) Ma, Y.; Guo, X.; Wu, X.; Dai, L.; Tong, L. Semiconductor nanowire lasers. Adv. Opt. Photonics 2013, 5, 216–273. 13 ACS Paragon Plus Environment

ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(18) Zimmler, M. A.; Capasso, F.; M¨ uller, S.; Ronning, C. Optically pumped nanowire lasers: invited review. Semicond. Sci. Technol. 2010, 25, 024001. (19) Seo, M. A.; Yoo, J.; Dayeh, S. A.; Picraux, S. T.; Taylor, A. J.; Prasankumar, R. P. Mapping carrier diffusion in single silicon core-shell nanowires with ultrafast optical microscopy. Nano Lett. 2012, 12, 6334–6338. (20) Gabriel, M. M.; Kirschbrown, J. R.; Christesen, J. D.; Pinion, C. W.; Zigler, D. F.; Grumstrup, E. M.; Mehl, B. P.; Cating, E. E. M.; Cahoon, J. F.; Papanikolas, J. M. Direct Imaging of Free Carrier and Trap Carrier Motion in Silicon Nanowires by SpatiallySeparated Femtosecond Pump-Probe Microscopy. Nano Lett. 2013, 13, 1336–1340. (21) Pf¨ uller, C.; Brandt, O.; Flissikowski, T.; Chèze, C.; Geelhaar, L.; Grahn, H. T.; Riechert, H. Statistical analysis of excitonic transitions in single, free-standing GaN nanowires: Probing impurity incorporation in the poissonian limit. Nano Res. 2010, 3, 881–888. (22) Seo, M. A.; Dayeh, S. A.; Upadhya, P. C.; Martinez, J. A.; Swartzentruber, B. S.; Picraux, S. T.; Taylor, A. J.; Prasankumar, R. P. Understanding ultrafast carrier dynamics in single quasi-one-dimensional Si nanowires. Appl. Phys. Lett. 2012, 100, 071104. (23) Choi, C. K.; Little, B. D.; Kwon, Y. H.; Lam, J. B.; Song, J. J.; Chang, Y. C.; Keller, S.; Mishra, U. K.; DenBaars, S. P. Femtosecond pump-probe spectroscopy and time-resolved photoluminescence of an Inx Ga1−x N/GaN double heterostructure. Phys. Rev. B 2001, 63, 195302. (24) Omae, K.; Kawakami, Y.; Narukawa, Y.; Watanabe, Y.; Mukai, T.; Fujita, S. Nondegenerated Pump and Probe Spectroscopy in InGaN-Based Semiconductors. Phys. Status Solidi A 2002, 190, 93–98. (25) Kawakami, Y.; Narukawa, Y.; Omae, K.; Fujita, S.; Nakamura, S. Dynamics of optical


Page 14 of 20

Page 15 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

gain in Inx Ga1−x N multi-quantum-well-based laser diodes. Appl. Phys. Lett. 2000, 77, 2151–2153. ¨ ur, U.; ¨ Everitt, H. O. Ultrafast carrier relaxation in GaN, In0.05 Ga0.95 N and an (26) Ozg¨ In0.07 Ga0.93 N/In0.12 Ga0.88 N multiple quantum well. Phys. Rev. B 2003, 67, 155308. (27) Satake, A.; Masumoto, Y.; Miyajima, T.; Asatsuma, T.; Ikeda, M. Two-dimensional exciton dynamics and gain formation processes in Inx Ga1−x N multiple quantum wells. Phys. Rev. B 1999, 60, 16660. (28) Hangleiter, A.; Jin, Z.; Gerhard, M.; Kalincev, D.; Langer, T.; Bremers, H.; Rossow, U.; Koch, M.; Bonn, M.; Turchinovich, D. Efficient formation of excitons in a dense electron-hole plasma at room temperature. Phys. Rev. B 2015, 92, 241305. (29) van Capel, P.; Turchinovich, D.; Porte, H. P.; Lahmann, S.; Rossow, U.; Hangleiter, A.; Dijkhuis, J. Correlated terahertz acoustic and electromagnetic emission in dynamically screened InGaN/GaN quantum wells. Phys. Rev. B 2011, 84, 085317. (30) Upadhya, P. C.; Li, Q.; Wang, G. T.; Fischer, A. J.; Taylor, A. J.; Prasankumar, R. P. The influence of defect states on non-equilibrium carrier dynamics in GaN nanowires. Semicond. Sci. Technol. 2010, 25, 024017. (31) Kar, A.; Li, Q.; Upadhya, P. C.; Seo, M. A.; Wright, J.; Luk, T.; Wang, G. T.; Prasankumar, R. P. The influence of radial heterostructuring on carrier dynamics in gallium nitride nanowires. Appl. Phys. Lett. 2012, 101, 143104. (32) You, G.; Liu, J.; Jiang, Z.; Wang, L.; El-Masry, N.; Hosalli, A.; Bedair, S. M.; Xu, J. Enhanced radiative recombination and suppressed Auger process in semipolar and nonpolar InGaN/GaN quantum wells grown over GaN nanowires. Opt. Lett. 2014, 39, 1501–1504.


ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(33) Ebaid, M.; Kang, J.-H.; Lim, S.-H.; Ko, S.-M.; Cho, Y.-H.; Ryu, S.-W. Ultrashort carrier lifetime of vapor–liquid–solid-grown GaN/InGaN multi-quantum-well coaxial nanorods. Acta Mater. 2014, 65, 118–124. (34) Pu, Y.-C.; Kibria, M.; Mi, Z.; Zhang, J. Z. Ultrafast Exciton Dynamics in InGaN/GaN and Rh/ Crn2 O3 Nanoparticle-Decorated InGaN/GaN Nanowires. J. Phys. Chem. Lett. 2015, 6, 2649–2656. (35) Upadhya, P. C.; Martinez, J. A.; Li, Q.; Wang, G. T.; Swartzentruber, B. S.; Taylor, A. J.; Prasankumar, R. P. Space-and-time-resolved spectroscopy of single GaN nanowires. Appl. Phys. Lett. 2015, 106, 263103. (36) Seo, M.; Boubanga-Tombet, S.; Yoo, J.; Ku, Z.; Gin, A.; Picraux, S.; Brueck, S.; Taylor, A.; Prasankumar, R. Ultrafast optical wide field microscopy. Opt. Express 2013, 21, 8763–8772. (37) Grumstrup, E. M.; Gabriel, M. M.; Cating, E. E.; Van Goethem, E. M.; Papanikolas, J. M. Pump–probe microscopy: Visualization and spectroscopy of ultrafast dynamics at the nanoscale. Chem. Phys. 2015, 458, 30–40. (38) Seo, M.; Yamaguchi, H.; Mohite, A. D.; Boubanga-Tombet, S.; Blancon, J.-C.; Najmaei, S.; Ajayan, P. M.; Lou, J.; Taylor, A. J.; Prasankumar, R. P. Ultrafast optical microscopy of single monolayer molybdenum disulfide flakes. Sci. Rep. 2016, 6, 21601. (39) Hartland, G. V. Ultrafast studies of single semiconductor and metal nanostructures through transient absorption microscopy. Adv. Opt. Photonics 2010, 1, 303–309. (40) Li, Q.; Westlake, K. R.; Crawford, M. H.; Lee, S. R.; Koleske, D. D.; Figiel, J. J.; Cross, K. C.; Fathololoumi, S.; Mi, Z.; Wang, G. T. Optical performance of top-down fabricated InGaN/GaN nanorod light emitting diode arrays. Opt. Express 2011, 19, 25528–25534.


Page 16 of 20

Page 17 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

(41) Li, Q.; Wright, J. B.; Chow, W. W.; Luk, T. S.; Brener, I.; Lester, L. F.; Wang, G. T. Single-mode GaN nanowire lasers. Opt. Express 2012, 20, 17873–17879. (42) Li, T.; Wei, Q.; Fischer, A.; Huang, J.; Huang, Y.; Ponce, F.; Liu, J.; Lochner, Z.; Ryou, J.-H.; Dupuis, R. The effect of InGaN underlayers on the electronic and optical properties of InGaN/GaN quantum wells. Appl. Phys. Lett. 2013, 102, 041115. (43) Riley, J. R.; Padalkar, S.; Li, Q.; Lu, P.; Koleske, D. D.; Wierer, J. J.; Wang, G. T.; Lauhon, L. J. Three-dimensional mapping of quantum wells in a GaN/InGaN core–shell nanowire light-emitting diode array. Nano lett. 2013, 13, 4317–4325. (44) Yang, C.-Y.; Chia, C.-T.; Chen, H.-Y.; Gwo, S.; Lin, K.-H. Ultrafast carrier dynamics in GaN nanorods. Appl. Phys. Lett. 2014, 105, 212105. (45) Tsokkou, D.; Othonos, A.; Zervos, M. Defect states of chemical vapor deposition grown GaN nanowires: Effects and mechanisms in the relaxation of carriers. Journal of Applied Physics 2009, 106, 054311–054311. (46) Armstrong, A. M.; Bryant, B. N.; Crawford, M. H.; Koleske, D. D.; Lee, S. R.; Wierer Jr, J. J. Defect-reduction mechanism for improving radiative efficiency in InGaN/GaN light-emitting diodes using InGaN underlayers. Journal of Applied Physics 2015, 117, 134501. (47) Leung, M. M.; Djuriˆsić, A. B.; Li, E. H. Refractive index of InGaN/GaN quantum well. Journal of Applied Physics 1998, 84, 6312–6317. (48) Robel, I.; Bunker, B. A.; Kamat, P. V.; Kuno, M. Exciton recombination dynamics in CdSe nanowires: bimolecular to three-carrier Auger kinetics. Nano Lett. 2006, 6, 1344–1349. (49) Htoon, H.; Hollingsworth, J.; Dickerson, R.; Klimov, V. I. Effect of zero-to one-


ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

dimensional transformation on multiparticle auger recombination in semiconductor quantum rods. Phys. Rev. Lett. 2003, 91, 227401. (50) Grumstrup, E. M.; Cating, E. M.; Gabriel, M. M.; Pinion, C. W.; Christesen, J. D.; Kirschbrown, J. R.; Vallorz III, E. L.; Cahoon, J. F.; Papanikolas, J. M. Ultrafast carrier dynamics of silicon nanowire ensembles: the impact of geometrical heterogeneity on charge carrier lifetime. J. Phys. Chem. C, 2014, 118, 8626–8633. (51) Zheng, J.; Kwok, H. Exciton and biexciton recombination in semiconductor nanocrystals. Appl. Phys. Lett. 1994, 65, 1151–1153. (52) Burda, C.; Link, S.; Mohamed, M. B.; El-Sayed, M. The pump power dependence of the femtosecond relaxation of CdSe nanoparticles observed in the spectral range from visible to infrared. J. Chem. Phys. 2002, 116, 3828–3833. (53) Roberti, T. W.; Cherepy, N. J.; Zhang, J. Z. Nature of the power-dependent ultrafast relaxation process of photoexcited charge carriers in II-VI semiconductor quantum dots: Effects of particle size, surface, and electronic structure. J. Chem. Phys. 1998, 108, 2143–2151. (54) Prasankumar, R. P.; Upadhya, P. C.; Taylor, A. J. Ultrafast carrier dynamics in semiconductor nanowires. Phys. Status Solidi B 2009, 246, 1973–1995. (55) Giblin, J.; Protasenko, V.; Kuno, M. Wavelength sensitivity of single nanowire excitation polarization anisotropies explained through a generalized treatment of their linear absorption. ACS Nano 2009, 3, 1979–1987. (56) Klimov, V. I. Optical nonlinearities and ultrafast carrier dynamics in semiconductor nanocrystals. J. Phys. Chem. B 2000, 104, 6112–6123. (57) Zhang, M.; Bhattacharya, P.; Singh, J.; Hinckley, J. Direct measurement of auger recombination in In0.1 Ga0.9 N/GaN quantum wells and its impact on the efficiency of 18 ACS Paragon Plus Environment

Page 18 of 20

Page 19 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Photonics

In0.1 Ga0.9 N/GaN multiple quantum well light emitting diodes. Appl. Phys. Lett. 2009, 95, 1108. (58) Meneghini, M.; Trivellin, N.; Meneghesso, G.; Zanoni, E.; Zehnder, U.; Hahn, B. A combined electro-optical method for the determination of the recombination parameters in InGaN-based light-emitting diodes. Journal of Applied Physics 2009, 106, 114508. (59) Brendel, M.; Kruse, A.; Jönen, H.; Hoffmann, L.; Bremers, H.; Rossow, U.; Hangleiter, A. Auger recombination in GaInN/GaN quantum well laser structures. Appl. Phys. Lett. 2011, 99, 031106. (60) Guo, W.; Zhang, M.; Bhattacharya, P.; Heo, J. Auger recombination in III-nitride nanowires and its effect on nanowire light-emitting diode characteristics. Nano Lett. 2011, 11, 1434–1438. (61) Sun, C.-K.; Keller, S.; Wang, G.; Minsky, M.; Bowers, J.; DenBaars, S. Radiative recombination lifetime measurements of InGaN single quantum well. Appl. Phys. Lett. 1996, 69, 1936–1938. (62) Puthussery, J.; Lan, A.; Kosel, T. H.; Kuno, M. Band-filling of solution-synthesized CdS nanowires. ACS Nano 2008, 2, 357–367. (63) Davies, M.; Dawson, P.; Hammersley, S.; Zhu, T.; Kappers, M.; Humphreys, C.; Oliver, R. Comparative studies of efficiency droop in polar and non-polar InGaN quantum wells. Appl. Phys. Lett. 2016, 108, 252101. (64) Piprek, J. Efficiency droop in nitride-based light-emitting diodes. Phys. Status Solidi A 2010, 207, 2217–2225. (65) Zhang, S.; Li, Y.; Fathololoumi, S.; Nguyen, H. P. T.; Wang, Q.; Mi, Z.; Li, Q.; Wang, G. T. On the efficiency droop of top-down etched InGaN/GaN nanorod light emitting diodes under optical pumping. AIP Adv. 2013, 3, 082103. 19 ACS Paragon Plus Environment

ACS Photonics

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Graphical TOC Entry


Page 20 of 20

Ultrafast Carrier Capture and Auger ... - ACS Publications

Recommend Documents