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Surfaces, Interfaces, and Applications
Insight into the near-conduction band states at the crystallized interface between GaN and SiNx grown by low-pressure chemical vapor deposition Xinyu Liu, Xinhua Wang, Yange Zhang, Ke Wei, Yingkui Zheng, Xuanwu Kang, Haojie Jiang, Junfeng Li, Wenwu Wang, Xuebang Wu, Xian Ping Wang, and Sen Huang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b04694 • Publication Date (Web): 04 Jun 2018 Downloaded from http://pubs.acs.org on June 4, 2018
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ACS Applied Materials & Interfaces
Insight into the near-conduction band states at the crystallized interface between GaN and SiNx grown by low-pressure chemical vapor deposition Xinyu Liu,† Xinhua Wang,*,†,‡ Yange Zhang,# Ke Wei,† Yingkui Zheng,† Xuanwu Kang,† Haojie Jiang,§ Junfeng Li,§ Wenwu Wang,§ Xuebang Wu,# Xianping Wang,**,# and Sen Huang***,†,‡
†
High-Frequency High-Voltage Device and Integrated Circuits R&D Center, Institute of
Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
‡
Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of
Microelectronics, Chinese Academy of Sciences, Key Laboratory of Microelectronic Devices & Integrated Technology, Beijing, 100029, China
§
Integrated Circuit Advanced Process Center, Institute of Microelectronics, Chinese Academy of
Sciences, Key Laboratory of Microelectronic Devices & Integrated Technology, Beijing, 100029, China
#
Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, China
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ABSTRACT. Constant-capacitance deep-level transient Fourier spectroscopy is utilized to characterize the interface between a GaN epitaxial layer and a SiNx passivation layer grown by low-pressure chemical vapor deposition (LPCVD). A near-conduction band (NCB) state ELP (EC-ET = 60 meV) featuring a very small capture cross section of 1.5×10-20 cm-2 was detected at 70 K at the LPCVD-SiNx/GaN interface. A partially crystallized Si2N2O thin layer was detected at the interface by high-resolution transmission electron microscopy. Based on first-principles calculations of crystallized Si2N2O/GaN slabs, it was confirmed that the NCB state ELP mainly originates from the strong interactions between the dangling bonds of gallium and its vicinal atoms near the interface. The partially crystallized Si2N2O interfacial layer might also give rise to the very small capture cross section of the ELP owing to the smaller lattice mismatch between the Si2N2O and GaN epitaxial layer and a larger mean free path of the electron in the crystallized portion compared with an amorphous interfacial layer.
KEYWORDS. GaN; Capture cross section; Constant-capacitance deep-level transient Fourier spectroscopy; First-principles; Interface states; LPCVD-SiNx; Near-conduction band states; Si2N2O
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ACS Applied Materials & Interfaces
Introduction
GaN-based high-electron-mobility transistors (HEMTs) have demonstrated great potential in RF/microwave and power switching applications due to advanced material properties such as the wide bandgap, high electron mobility and high electron density.1, 2 The passivation of the surface states on the AlGaN/GaN heterostructure plays a crucial role in the suppression of the current collapse in power amplifiers or the degradation of the dynamic on-resistance (RON) in power switches.3,
4
In general, the density (Dit) of the deep states on the (Al)GaN surface can be
effectively suppressed to the order of 1011-1012 cm-2 eV-1, by a passivation layer such as SiO2, 5, 6 SiNx,7-13 and AlN,4 etc. In particular, SiNx dielectrics grown by low-pressure chemical vapor deposition (LPCVD), which feature excellent TDDB properties and a robust SiNx/AlGaN interface with low deep interface states, 9, 10, 12-15 could be a compelling gate/passivation dielectric for
one
of
the
next-generation
GaN-based
power
devices,
the
metal-insulator(oxide)-semiconductor HEMT (MIS/MOS-HEMT).
However, the states located close to the conduction band (EC) of (Al)GaN are still relatively high and is commonly higher than 1013 cm-2 eV-1.12, 15-18 Due to few report about the experimental value of the capture cross section (σn),
19, 20
σn is typically inadequately assumed to be constant
across the whole interface at a value of 10-14-10-16 cm-2.16 Such an assumption would enormously underestimate the emission time constant (τe), which could give rise to a current collapse at low frequencies (e.g.,
