Optically pumped GeSn lasers operating at 270 K with broad

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Optically pumped GeSn lasers operating at 270 K with broad waveguide structures on Si Yiyin Zhou, Wei Dou, Wei Du, Solomon Ojo, Huong Tran, Seyed A. Ghetmiri, Jifeng Liu, Greg Sun, Richard Soref, Joe Margetis, John Tolle, Baohua Li, Zhong Chen, Mansour Mortazavi, and Shui-Qing Yu ACS Photonics, Just Accepted Manuscript • DOI: 10.1021/acsphotonics.9b00030 • Publication Date (Web): 15 May 2019 Downloaded from http://pubs.acs.org on May 15, 2019

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Optically pumped GeSn lasers operating at 270 K with broad waveguide structures on Si Yiyin Zhou1,2,3, Wei Dou1, Wei Du4, Solomon Ojo1,2, Huong Tran1,3, Seyed A. Ghetmiri5, Jifeng Liu6, Greg Sun7, Richard Soref7, Joe Margetis8, John Tolle8, Baohua Li3, Zhong Chen1, Mansour Mortazavi5, Shui-Qing Yu1† 1Department of Electrical Engineering, University of Arkansas, Fayetteville, Arkansas 72701 USA 2Microelectonics-Photonics 3Arktonics,

Program, University of Arkansas, Fayetteville, Arkansas 72701 USA

LLC, 1339 South Pinnacle Drive, Fayetteville, Arkansas 72701 USA

4Department

of Electrical Engineering, Wilkes University, Wilkes-Barre, Pennsylvania 18766

USA 5Department

of Chemistry and Physics, University of Arkansas at Pine Bluff, Pine Bluff, Arkansas

71601 USA 6Thayer

School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 USA

7Department

of Engineering, University of Massachusetts Boston, Boston, Massachusetts 02125

USA 8ASM,

3440 East University Drive, Phoenix, Arizona 85034, USA

†Corresponding

author

Abstract Lasing from direct bandgap group-IV GeSn alloys has opened a new venue for the development of Si-based monolithic laser. In this work, we demonstrate optically pumped GeSn lasers based on both ridge and planar waveguide structures. The near room temperature operation at 270 K was achieved with optically pumped edge-emitting devices. Moreover, due to the reduced sidewall surface recombination and improved thermal management, the 100-µm-width ridge waveguide laser features a lower lasing threshold compared to other devices. The advance reported in this work, enabled by the material growth via an industry standard chemical vapor 1 ACS Paragon Plus Environment

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deposition reactor and low-cost commercially available precursors, is a major step forward towards Si-based mid-infrared sources for photonics integration. Keywords: GeSn laser, mid-infrared, Si photonics, planar waveguide laser

Tremendous efforts for broadening the reach of current Si technology have been directed to build integrated photonics over the past few decades.1-3 Among the many devices including light emitters, amplifiers, photodetectors, waveguides, modulators, couplers, and switches that make up a complete set of components for Si photonics, a monolithically integrated light source on Si has long been desired to address the deficiency in high efficiency and reliability emitters for the nextgeneration photonic integrated circuit on the Si platform.4-6 However, group-IV materials such as Si, Ge, and SiGe alloys have been largely excluded from being selected into making efficient light sources due to their indirect bandgap. Although optically pumped rare-earth-doped lasers7-9 and Si Raman laser10 have been reported, they are low in efficiency and do not rely on bandgap emission and cannot be operated under direct electrical pumping. The Ge laser first reported in 2010 employed strain-engineering and heavy n-type doping to compensate for its indirect bandgap, featuring high lasing threshold and fabrication difficulties.11 Currently, Si photonics utilizes direct bandgap III-V lasers as light sources via various non-monolithic integration approaches such as wafer-bonding or direct-growth.12-17 Recently, the studies on group-IV GeSn alloy open a new opportunity towards the possibility of attaining monolithic laser sources integrated on Si with full complementary metal-oxidesemiconductor (CMOS) compatibility, as the true direct bandgap GeSn has been experimentally identified in 2014 and the first optically pumped laser has been demonstrated in early 2015.18,19 Since then, the GeSn laser results have been reported by various research groups worldwide.20-29

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Laser devices based on various structures engineered to facilitate population inversion, carrier and optical confinement, such as double heterostructure (DHS),20 multi-quantum-well (MQW),26-28 and microdisk configurations have been demonstrated.29 Although the device performance has since been dramatically improved in terms of lasing threshold and operation temperature,21,27,29 the highly desired room temperature or near room temperature lasing operation has not been achieved yet. In this work, GeSn lasers based on the ridge and planar waveguide structures are investigated via optical pumping. The 20% Sn composition yields direct bandgap GeSn alloy with its Γ valley sitting more than 100 meV below its L valley in the conduction band. The maximum lasing operation temperature was achieved at 270 K, being evidenced by the laser-output versus pumping-laser-input (L-L) curves and the emission spectra. The lowest lasing threshold was obtained from the 100-µm-width ridge waveguide structure. Further analysis revealed that the improved local heating dissipation and reduced surface recombination of the 100-µm-width ridge device lead to the high lasing operation temperature and lower threshold. With the current lasing temperature being close to the room temperature, it is essential in the future to switch from the bulk to more advanced device structures such as multiple quantum wells for electrical injection operation30, as suggested in ref. 30 that with a possible active region design of 20 SiGeSn/GeSn QWs. The GeSn sample was grown on a relaxed Ge buffer (nominal 700-nm-thick) on a Si substrate using an industry-standard ASM Epsilon® 2000 PLUS reduced pressure chemical vapor deposition (RPCVD) reactor with commercially available precursors of GeH4 and SnCl4. A multiple-step Sn-enhanced growth recipe was used to achieve a 20% final Sn composition, which was developed and reported in our previous study regarding spontaneous-relaxation-enhanced


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(SRE) Sn incorporation process.31 Note that by using the compensated Sn incorporation approach, i.e., adjusting the SnCl4 flow to compensate the increased Sn incorporation, the constant Sn incorporation is able to be achieved.32 After growth, Sn composition was determined by secondary ion mass spectrometry (SIMS); the strain was extracted by reciprocal space mapping (RSM) of Xray diffraction (XRD) measurement; the GeSn thickness and material quality were studied by transmission electron microscopy (TEM) image. The SIMS and XRD 2θ-ω scan were also used to cross-check the layer thicknesses and the Sn compositions. RESULTS AND DISCUSSION

Figure 1. (a)TEM image of sample showing 1st defective relaxing layer and 2nd high quality GeSn top layer, which acts as the gain region. (b) SIMS profile of Sn composition with the three regions indicated; (c) XRD RSM contour map showing the graded Sn composition in 1st and 2nd GeSn layers.

Material characterization. Figure 1a shows the high-resolution TEM image of the sample. The Ge and GeSn layers are clearly shown. For GeSn alloy, two distinct layers can be observed, as marked as the 1st and 2nd layers with the thicknesses of 450 nm and 970 nm, respectively. The 1st layer over the Ge buffer is defective due to the relatively high threading dislocation density (TDD) as a result of lattice mismatch between Ge and GeSn. However, the formation of threading 4 ACS Paragon Plus Environment

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dislocation loops in the 1st GeSn layer prevents the defects from propagating into the 2nd GeSn layer, as shown in Fig. 1a. As a result, the 2nd GeSn layer exhibits relatively low TDD of 106 cm2

according to the etch pit density measurement.

The formation mechanism of threading

dislocation loops was discussed in our previous studies.33,34 The SIMS result is shown in Fig. 1b. Three regions can be resolved based on Sn incorporation: i) region I with the constant Sn composition of 11% and thickness of 200 nm; (ii) region II with the Sn-composition grading rate of 17.4%/µm and thickness of 230 nm, leading to increase of Sn composition from 11% to 15%; iii) region III with the Sn-composition grading rate of 5.2%/µm and thickness of 970 nm, resulting in maximum Sn incorporation of 20% at the surface. The graded Sn incorporation can be explained as the following: the GeSn growth starts with a nominal 11% Sn recipe, once the layer thickness reaches its critical thickness, the gradual relaxation of the material facilitates more Sn incorporation, resulting in subsequent Sn incorporation in the GeSn layer increases to 20%. Note that the combination of regions I and II corresponds to 1st layer observed in TEM, while the region III corresponds to 2nd layer. Figure 1c shows the RSM contour plot of the GeSn. The 1st and 2nd layers can be clearly resolved. The dashed line indicates the strain relaxation line. The broadened contour plot is mainly due to the graded Sn compositions in each layer. Since it is very difficult to pinpoint the strain at a specific point due to the graded Sn composition, the averaged strain at each GeSn layer was extracted, as -0.10% and -0.52% for the 1st and 2nd layer, respectively.


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Figure 2. (a) Temperature-dependent PL spectra using 532 nm CW laser pumping.

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(b)

Temperature-dependent FWHM and normalized integrated intensity of PL spectra.

The temperature-dependent photoluminescence (PL) measurements were performed using a 532-nm excitation laser to study the optical property of the GeSn layer. Figure 2a shows the temperature-dependent PL spectra. As the temperature decreases from 300 K to 10 K, the PL intensity significantly increases, indicating the unambiguous signature of the direct bandgap material. The “three peaks” feature in PL spectra is due to the H2O and CH4 absorptions at 3.0 μm and 3.2 μm, respectively, which result in two valleys in spectra. The PL peak blue-shift following the Varshni empirical model was observed as expected. Note that the optical transitions, i.e., light absorption and emission are mainly limited to the near-surface region, where the Sn composition is ~20%. This is due to: i) the penetration depth of the 532-nm excitation laser is less than 50 nm; and ii) the photogenerated carriers tend to transport from the wider bandgap region (GeSn region away from the surface) to the narrower bandgap region (surface) as the result of the graded Sn composition. Further PL peak analysis was conducted using Lorentzian function fitting. From 300 to 10 K, the integrated PL intensity increases up to 35 times and the PL peak full width half 6 ACS Paragon Plus Environment

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maximum (FWHM) decreases rapidly from 74 to 28 meV, as shown in Fig. 2b, suggesting that the PL emission originates from the band-to-band radiative recombination in the direct bandgap.

Figure 3. Pumping laser beam profile compared with devices with different ridge widths.

Device fabrication and pumping power density calculation. Laser devices based on the ridge and planar waveguide structures were investigated. The ridge waveguides with ridge widths of 5, 20, and 100 µm (annotated as devices A, B, and C) were fabricated by standard photolithography and wet chemical etching processes that were developed by our previous work22 while the planar structure (annotated as device D) was not etched at all. The etching depth was selected as 800 nm to provide sufficient mode confinement. All samples including ridge and planar waveguides were lapped down to ~70 μm thickness and then cleaved to form the cavity with the lengths of 2750 (device A, B and C) and 2650 μm (devices D). The optical pumping characterization was performed using two excitation sources: a pulsed 1064-nm laser and a pulsed 1950-nm laser. To accurately calculate the effective light absorption for each device as they feature different ridge width, the cross-sectional profile of the pumping laser beam was measured, as shown in Fig. 3. The pumping power density was calculated in the following way: cross-sectional profile of each laser beam was measured and then fitted using 7 ACS Paragon Plus Environment

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Lorentzian function. For the device whose ridge width is smaller than the FWHM of the laser beam, the overall pumping power intensity was calculated by the integral of power within the ridge region divided by the product of ridge width and cavity length. For the device whose ridge width is wider than the FWHM including the planar waveguide device, the pumping power density was calculated according to total excitation power / FWHM. The effective light absorption for each device is summarized in Table I.

TABLE I. Spatial overlap percentage between device and pump laser calculated from beam spot profile and device geometry Device A

Device B

Device C

Device D

Ridge width

5 μm

20 μm

100 μm

Planar

1064 nm laser

14.2%

47.0%

86.2%

100%

1950 nm laser

18.2%

55.2%

89.3%

100%

Laser characterization using 1064 nm excitation source. The optical pumping characterization was firstly performed using a pulsed 1064 nm laser. The L-L curves for each sample were measured from 77 K to its maximum operating temperature. The typical L-L curves at different temperatures are shown in Fig. 4a for device C.


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Figure 4. L-L curves under 1064 nm laser excitation. (a) from 77 to 260 K for device C; (b) all devices at 77 K; and (c) devices B, C, and D at 260 K.

At 77 K, the lasing thresholds were extracted as 516, 384, 356, and 330 kW/cm2 for devices A, B, C, and D, respectively (Fig. 4b), exhibiting lower thresholds of wider ridge devices B, C and D than that of device A. Note that the spatial distribution of the light absorption shown in Table I was taken into account for the threshold calculations. Moreover, since the excitation is not uniform, the net positive gain may be achieved in the middle of the waveguide but not at the edges, resulting in the enhanced spontaneous emission and consequently the gradual transition of threshold behavior. The reduced threshold with wider ridge devices could be attributed to the reduced surface recombination: the increase of ridge width leads to less effect from the side wall surface recombination. For device A, the maximum operating temperature was measured at 120 K; while for devices B, C, and D, 260 K lasing temperature was obtained (Fig. 4c), which is higher than previously reported highest ridge waveguide lasers (180 K) and microdisk lasers (230 K).22, 29 The higher operating temperature obtained is mainly due to the high material quality that was achieved using our unique growth recipe30 as well as the 65.4% modal overlap (for B and C. For A: 64.9%; 9 ACS Paragon Plus Environment

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D: 65.6%) with the low TDD GeSn gain region. Moreover, the increased operating temperature of devices B, C, and D featuring wider ridges and/or planar structure is made possible thanks to the improved heat dissipation compared to device A that with a narrower ridge, suffering from the enhanced free carrier absorption. At 260 K, the lasing thresholds were extracted as 2990, 6055, and 9587 kW/cm2 for devices B, C, and D, respectively, showing the trend of threshold increase as ridge width increases. This can be interpreted by that: i) the dramatically increased free carrier absorption and non-radiative recombination at higher temperature dominate the loss over the side wall surface recombination; ii) the inhomogeneous excitation for a wider cavity device could result in achieving gain in the middle of the waveguide but not at the edges, where light absorption could occur; and iii) the less optical confinement of sample D also leads to its higher threshold.

Figure 5. Lasing spectra at 2 × threshold under the excitation of 1064 nm laser for devices (a) A; (b) B; (c) C; and (d) D. The PL spectra (dashed curves) are also plotted for comparison.

Lasing spectra were measured at 2-times lasing threshold pumping power density of each sample. Due to the relatively large area of the cavity facet, the typical multimode lasing characteristic was observed for each device. In Fig. 5, each resolved peak actually consists of 10 ACS Paragon Plus Environment

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multiple peaks that are mostly overlapped, which cannot be further identified from the spectrum owing to the resolution limit of the spectrometer of ~0.1 nm considering the transverse and longitudinal mode spacings of 0.01 and 1.3 nm, respectively. Despite the mode overlapping, the FWHM of each resolved peak was estimated as ~2 to 3 meV. Compared with the FWHM of PL spectra at 10 K of 23 meV shown in Fig. 2, the significantly decreased FWHM indicates the unambiguous signature of lasing. At 77 K, the lasing wavelengths were obtained from 2641 to 2961 nm for devices A-D. Compared with the PL peak at 3250 nm at 77 K, the clear peak blue-shift was observed, which might be interpreted as the typical band-filling effect dominant under intense injection. Device A exhibits more blue-shift than the other three samples due to the higher pumping power density that results in higher energy levels being populated by carriers in both conduction and valence bands. As temperature increases from 77 to 260 K, the lasing peak all shifts towards longer wavelength for devices B, C, and D as expected. It is worth noting that as the temperature increases from 77 K, the separation between lasing and PL peak gradually reduces, and eventually the lasing peak occurs at a longer wavelength than PL peak beyond 160 K. At 260 K, the lasing peaks for devices B, C, and D locate at ~3330 nm, which is longer than PL peak. This might be explained as follows: the main factors affecting the lasing peak shift include: i) the higher pumping intensity compared to that in PL measurement results in the high density of carriers that contributes to the band-filling effect which in turn results in the blue-shift of the lasing peaks; ii) the increased temperature leads to the red-shift of lasing peak; and iii) the shift of gain spectrum due to bandgap altering with temperature results in the lasing peak shift. Note that other factors such as refractive index altering with temperature could also affect the lasing position. Therefore, the lasing peak shift is an overall effect of competition among the factors above mentioned. At lower temperatures, the band-filling


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effect could dominate the peak shift, results in the overall blue-shift; while at higher temperatures, the increased temperature might become the dominant factor, as a result, the overall red-shift was observed. For device C, the 77 K spectrum shows two more peaks at ~2750 and ~3300 nm in addition to the main lasing peak, which might be due to the non-uniform distribution of the modal gain at 77 K, leading to extra enhanced modes in the lasing output. The similar peak feature can also be observed from device D at 77 K and around ~2800 nm, as shown in Fig. 5d. Laser characterization using 1950 nm excitation source. Since the pumping photon energy of 1064 nm laser (1.165 eV) is much higher than the emission photon energy (less than 0.469 eV), the large quantum defect, i.e., the energy difference between absorbed and emitted photons could lead to deterioration of lasing performance by local heating. To reduce the impact of the quantum defect on lasing characteristics, a 1950-nm laser was used as the excitation source.

Figure 6. L-L curves under 1950 nm laser excitation. (a) from 77 to 270 K for device C; (b) all devices at 77 K; and (c) devices B, C, and D at 270 K. The dotted lines indicate the method of threshold extraction.


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Figure 6a shows the typical L-L curves at different temperatures for device C. For device A, the maximum operating temperature increases from 120 to 140 K; while for devices B, C, and D, their maximum operating temperatures are increased to near room temperature at 270 K. At 77 K, the lasing thresholds were extracted as 132, 88, 47, 74 kW/cm2 for devices A, B, C, and D, respectively, much smaller than those under 1064-nm laser excitation even with a lower absorption coefficient of 1950 nm. We attribute the increased operating temperature and dramatically reduced thresholds to the following: the quantum defect of ~170 meV is 45% smaller for the 1950-nm laser compared to the 1064-nm laser of ~700 meV, and results in less excess phonon energy being converted into thermal energy under the 1950-nm pumping. For devices B, C, and D, the thresholds at their maximum operating temperatures are measured as 886, 796, and 1105 kW/cm2, respectively. It is worth pointing out that under 1950-nm laser pumping, due to the small quantum defect, the thermal effect reduces. Device C with 100-µm-wide ridge could offer comparable heat dissipation as device D while featuring better optical confinement as well as spatial carrier confinement than device D, leading to its lowest lasing threshold among all devices at each temperature.


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Figure 7. Lasing spectra at 2 × threshold under the excitation of 1950 nm laser for devices (a) A; (b) B; (c) C; and (d) D. The PL spectra (dashed curves) are also plotted for comparison.

Figure 7 shows the lasing spectra measured at 2-times lasing threshold pumping power density for each device. The multimode lasing characteristic was observed at each temperature. At 77 K, the lasing wavelengths were obtained from 2700 to 3270 nm for four devices. In Figs. 7b and 7c, the peak at ~3005 nm is possibly due to the non-uniform distribution of modal gain that was observed under 1064-nm laser pumping as well. For devices B, C, and D, the similar blue-shift of the lasing peak at a lower temperature and red-shift at a higher temperature relative to PL peak were observed, as the result of the band-filling effect and local heating effect being dominant at low and high temperatures, respectively. The lasing peaks at 3350~3450 nm were obtained for devices B, C, and D at their maximum operating temperature of 270 K, respectively. The lasing characterization results are summarized in Table II.


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TABLE II. Summary of lasing characterization 1064-nm pumping

A (5 μm)

B (20 μm)

C (100 μm)

D (Planar)

Threshold @77K (kW/cm2)

516

384

356

330

Peak position @77K (nm)

2641

2802

2965

2961

Maximum Operating Temperature (K)

120

260

260

260

Threshold @ Maximum Operating Temperature (kW/cm2)

903

2990

6055

9587

Peak position @ Maximum Operating Temperature (nm)

2970

3432

3444

3334

A (5 μm)

B (20 μm)

C (100 μm)

D (Planar)

Threshold @77K (kW/cm2)

132

88

47

74

Peak position @77K (nm)

2703

3022

3272

2997

Maximum Operating Temperature (K)

140

270

270

270

Threshold @ Maximum Operating Temperature (kW/cm2)

364

886

796

1105

Peak position @ Maximum Operating Temperature (nm)

2780

3414

3462

3354

1950-nm pumping

Stimulated emission study at 280 K. Device C was selected for further optical pumping characterization at 280 K. Under pumping power density of 3.1 MW/cm2, the spontaneous emission dominates the spectrum (The peak ~3900 nm is the artifact due to the second order diffraction of the 1950-nm pumping laser). As the pumping power density increases, a peak at ~3450 nm emerges, and its intensity increases dramatically with the pumping power density, as shown in Fig. 8. At 7.6 MW/cm2, this peak exhibits strong intensity and narrowed line-width of ~7 meV, showing the clear stimulated emission characteristics. While the pumping power density


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cannot be increased further due to the severe heat generation, we could not further confirm the lasing at 280 K.

Figure 8. Power-dependent emission spectra of sample C at 280 K under 1950 nm laser.

In conclusion, optically pumped GeSn lasers with ridge and planar waveguide structures were investigated. The GeSn sample was grown using a multiple-step Sn-enhanced growth recipe via industry standard CVD reactor with low-cost SnCl4 and GeH4 precursors. The maximum Sn composition of 20% was obtained. The maximum operating temperature of 270 K was achieved. At 280 K, stimulated emission spectrum was observed with intensive pumping power density. Our systemic study of the four optically pumped laser devices with various ridge width reveals that the reduced side-wall surface recombination and better heat dissipation are key factors to achieve near room temperature operation. We predict that room temperature GeSn lasers can be demonstrated by: i) surface passivation (adding Ge cap layer) to further reduce the surface recombination; and 16 ACS Paragon Plus Environment

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ii) optimization of the ridge width to strike a balance between the heat dissipation and optical confinement. Moreover, the demonstration of planar waveguide laser structure in this study points at the great potential of GeSn lasers being advanced towards high-performance Si-based monolithically integrated mid-infrared laser sources.

METHODS GeSn sample growth. A 750-nm-thick Ge buffer layer was first grown on Si followed by an insitu annealing to reduce the defects. A nominal 11% Sn based recipe was used to initiate the GeSn growth. The Sn incorporation starts from 11%. As the GeSn grows thicker, the gradually relaxed material leads to the Sn incorporation in subsequent GeSn layer increases until 15% with a grading rate of 17.4%/µm. This is the 1st GeSn layer, in which the formation of threading dislocation loops prevents the defects from being propagated to the subsequent 2nd GeSn layer. As the material almost fully relaxes, the Sn incorporation increases with a grading rate of 5.2%/µm, until the final Sn composition of 20% was achieved. This is the 2nd GeSn layer featuring low defect density. Photoluminescence (PL) measurements.

The PL measurements were performed using a

standard off-axis configuration with a lock-in technique (optically chopped at 377 Hz). A 532-nm continuous wave (CW) laser was used as an excitation source. The laser beam was focused down to a 100-μm-diam spot with the measured power of 100 mW. The PL emission was collected by a spectrometer and then was sent to an InSb detector with response cut-off at 5.0 μm. Optical pumping measurements. The optical pumping characterization was performed using two pulsed laser excitation sources: i) a 1064 nm laser with 10 kHz repetition rate and 2 ns pulse width; and ii) a 1950 nm laser with 10 kHz repetition rate and 20 ns pulse width. The laser beam was collimated to a narrow stripe (~20 µm width and 0.3 cm length) via a cylindrical lens to pump


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the GeSn waveguide devices. The device was first mounted on a Si chip carrier and then placed into a continuous flow cryostat for low-temperature measurement. The emission from the facet was collected by a spectrometer and then sent to an InSb detector. The integrated emission intensity was measured by setting the grating at zero order. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]

Acknowledgement The authors acknowledge financial support from the Air Force Office of Scientific Research (AFOSR) (Grant Nos. FA9550-18-1-0045, FA9550-16-C-0016, FA9550-14-1-0205, FA9550-171-0354), DoD Army Research Office with Grant Officer’s Representative Dr. Gernot Pomrenke from AFOSR (Grant No. W911NF-16-1-0517), and the Arkansas Biosciences Institute (ABI). We are thankful for Dr. M. Benamara’s assistance in TEM imaging and Dr. A. Kuchuk’s assistance in XRD measurement from Institute for Nanoscience & Engineering, University of Arkansas. Reference 1. Soref, R., The Past, Present, and Future of Silicon Photonics. IEEE Journal of Selected Topics in Quantum Electronics 2006, 12 (6), 1678-1687. 2. Soref, R., Mid-infrared photonics in silicon and germanium. Nature Photonics 2010, 4 (8), 495-497. 3. Soref, R.; Buca, D.; Yu, S.-Q., Group IV Photonics: Driving Integrated Optoelectronics. Optics and Photonics News 2016, 27 (1), 32-39. 4. Wang, X.; Liu, J., Emerging technologies in Si active photonics. Journal of Semiconductors 2018, 39 (6), 061001. 5. Heck, M. J. R.; Bowers, J. E., Energy Efficient and Energy Proportional Optical Interconnects for Multi-Core Processors: Driving the Need for On-Chip Sources. IEEE Journal of Selected Topics in Quantum Electronics 2014, 20 (4), 332-343. 6. Zhou, Z.; Yin, B.; Michel, J., On-chip light sources for silicon photonics. Light: Science &Amp; Applications 2015, 4, e358.


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22. Margetis, J.; Al-Kabi, S.; Du, W.; Dou, W.; Zhou, Y.; Pham, T.; Grant, P.; Ghetmiri, S.; Mosleh, A.; Li, B.; Liu, J.; Sun, G.; Soref, R.; Tolle, J.; Mortazavi, M.; Yu, S.-Q., Si-Based GeSn Lasers with Wavelength Coverage of 2–3 μm and Operating Temperatures up to 180 K. ACS Photonics 2018, 5 (3), 827-833. 23. Reboud, V.; Gassenq, A.; Pauc, N.; Aubin, J.; Milord, L.; Thai, Q. M.; Bertrand, M.; Guilloy, K.; Rouchon, D.; Rothman, J.; Zabel, T.; Pilon, F. A.; Sigg, H.; Chelnokov, A.; Hartmann, J. M.; Calvo, V., Optically pumped GeSn micro-disks with 16% Sn lasing at 3.1 μm up to 180 K. Applied Physics Letters 2017, 111 (9), 092101. 24. Buca, D.; Stange, D.; Schulte-Braucks, C. Wirths, S.; Driesch, N. v. d.; Mantl, S.; Grützmacher, D.; Geiger, R.; Zabel, T.; Sigg, H.; Marzban, B.; Witzens, J.; Ikonic, Z.; Hartmann, J. M. In GeSn lasers for monolithic integration on Si, 2015 IEEE Summer Topicals Meeting Series (SUM), 13-15 July 2015; pp 57-58. 25. Stange, D.; Driesch, N. v. d.; Zabel, T.; Armand-Pilon, F.; Marzban, B.; Rainko, D.; Hartmann, J.; Capellini, G.; Schroeder, T.; Sigg, H.; Witzens, J.; Grützmacher, D.; Buca, D. In Reduced threshold microdisk lasers from GeSn/SiGeSn heterostructures, 2017 IEEE 14th International Conference on Group IV Photonics (GFP), 23-25 Aug. 2017; pp 15-16. 26. Margetis, J.; Zhou, Y.; Dou, W.; Grant, P. C.; Alharthi, B.; Du, W.; Wadsworth, A.; Guo, Q.; Tran, H.; Ojo, S.; Abernathy, G.; Mosleh, A.; Ghetmiri, S. A.; Thompson, G. B.; Liu, J.; Sun, G.; Soref, R.; Tolle, J.; Li, B.; Mortazavi, M.; Yu, S.-Q., All group-IV SiGeSn/GeSn/SiGeSn QW laser on Si operating up to 90 K. Applied Physics Letters 2018, 113 (22), 221104. 27. Grützmacher, D.; Rainko, D.; Buca, D.; Driesch, N. v. d.; Ikonic, Z.; Stange, D.; Hartmann, J. M. In Low Pumping Threshold GeSn/SiGeSn Multiple Quatum Well Lasers, 2018 IEEE 15th International Conference on Group IV Photonics (GFP), 29-31 Aug. 2018; 2018; pp 1-2. 28. von den Driesch, N.; Stange, D.; Rainko, D.; Povstugar, I.; Zaumseil, P.; Capellini, G.; Schröder, T.; Denneulin, T.; Ikonic, Z.; Hartmann, J.-M.; Sigg, H.; Mantl, S.; Grützmacher, D.; Buca, D., Advanced GeSn/SiGeSn Group IV Heterostructure Lasers. Advanced Science 2018, 5 (6), 1700955. 29. Thai, Q. M.; Pauc, N.; Aubin, J.; Bertrand, M.; Chrétien, J.; Delaye, V.; Chelnokov, A.; Hartmann, J.-M.; Reboud, V.; Calvo, V., GeSn heterostructure micro-disk laser operating at 230 K. Optics Express 2018, 26 (25), 32500-32508. 30. Sun, G.; Soref R.; Cheng, H, Design of a Si-based lattice-matched room-temperature GeSn/GeSiSn multi-quantum-well mid-infrared laser diode. Optics Express 2010, 18 (19), 19957-19965. 31. Dou, W.; Zhou, Y.; Magretis, J.; Ghetmiri, S.; Al-Kabi, S.; Du, W.; Liu, J.; Sun, G.; Soref, R.; Tolle, J.; Li, B.; Mortazavi, M.; Yu, S.-Q, Optically pumped lasing at 3 μm from compositionally graded GeSn with tin up to 22.3%. Optics Letters 2018, 43 (19), 4558-4561. 32. Grant, P.; Margetis J.; Zhou, Y. ; Dou, W.; Abernathy, G.; Kuchuk, A.; Du, W.; Li, B.; Tolle, J.; Liu, J.; Sun, G.; Soref, R.; Mortazavi, M.; Yu, S.-Q, Direct bandgap type-I GeSn/GeSn quantum well on a GeSn- and Ge- buffered Si substrate. AIP Advances 2018 8, 025104. 33. Dou, W.; Benamara, M.; Mosleh, A.; Margetis, J.; Grant, P.; Zhou, Y.; Al-Kabi, S.; Du, W.; Tolle, J.; Li, B.; Mortazavi, M.; Yu, S.-Q., Investigation of GeSn Strain Relaxation and Spontaneous Composition Gradient for Low-Defect and High-Sn Alloy Growth. Scientific Reports 2018, 8, 5640. 34. Margetis, J.; Yu, S.-Q.; Bhargava, N.; Li, B; Du, W.; Tolle, J., Strain engineering in epitaxial Ge1−xSnx: a path towards low-defect and high Sn-content layers. Semiconductor Science and Technology 2017, 32 (12), 124006. 20 ACS Paragon Plus Environment

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Optically pumped GeSn lasers operating at 270 K with broad waveguide structures on Si Yiyin Zhou1,2,3, Wei Dou1, Wei Du4, Solomon Ojo1,2, Huong Tran1,3, Seyed A. Ghetmiri5, Jifeng Liu6, Greg Sun7, Richard Soref7, Joe Margetis8, John Tolle8, Baohua Li3, Zhong Chen1, Mansour Mortazavi5, Shui-Qing Yu1†

(left) TEM image of GeSn sample; (middle) Light output power versus pump laser power at temperatures up to 270 K; (right) Spectra of GeSn lasers from 77 to 270 K.


Optically pumped GeSn lasers operating at 270 K with broad

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