Hole traps and persistent photocapacitance in proton irradiated β-Ga2O3 films doped with Si

A Y Polyakov,F Ren,A V Chernykh,P B Lagov,I V Shchemerov,N B Smirnov,S J Pearton,T V Kulevoy

doi:10.1063/1.5042646

Abstract

Hole traps in hydride vapor phase epitaxy β-Ga2O3 films were studied by deep level transient spectroscopy with electrical and optical excitation (DLTS and ODLTS) and by photocapacitance and temperature dependence measurements. Irradiation with 20 MeV protons creates deep electron and hole traps, a strong increase in photocapacitance, and prominent persistent photocapacitance that partly persists above room temperature. Three hole-trap-like signals H1 [self-trapped holes (STH)], H2 [electron capture barrier (ECB)], and H3, with activation energies 0.2 eV, 0.4 eV, 1.3 eV, respectively, were detected in ODLTS. The H1 (STH) feature is suggested to correspond to the transition of polaronic states of STH to mobile holes in the valence band. The broad H2 (ECB) feature is due to overcoming of the ECB of the centers responsible for persistent photocapacitance for temperatures below 250 K. The H3 peak is produced by detrapping of holes from Ev + 1.3 eV hole traps believed to be related to gallium vacancy acceptors. One more deep acceptor with optical ionization threshold near 2.3 eV is likely responsible for high temperature persistent photocapacitance surviving up to temperatures higher than 400 K. The latter traps show a significant barrier for capture of electrons.

Highlights

The recent interest in β-Ga2O3 is driven by its excellent properties for high-temperature/highpower applications, light-transparent electronics, and solar-blind photodetectors.[1,2] The quality of bulk materials and epitaxial layers has improved dramatically in recent years,[1,2,3,4,5,6] and the technology for fabrication of Schottky diodes, photodetectors, and field effect transistors has greatly matured
Photocapacitance, deep level optical spectroscopy (DLOS), and optical deep level spectroscopy (ODLTS) experiments suggest the presence in the lower half of the bandgap of β-Ga2O3, a set of deep acceptor states, some of which show a strong electron-phonon coupling and can have considerable barriers for capture of nonequilibrium charge carriers.[12,13,14,15]
It has been reported that deep acceptors related to Ga vacancies could provide high temperature hole conductivity in β-Ga2O3.16 In this paper, these issues are studied for high-quality β-Ga2O3 films grown by hydride vapor phase epitaxy (HVPE)

Summary

Introduction

The recent interest in β-Ga2O3 is driven by its excellent properties for high-temperature/highpower applications, light-transparent electronics, and solar-blind photodetectors.[1,2] The quality of bulk materials and epitaxial layers has improved dramatically in recent years,[1,2,3,4,5,6] and the technology for fabrication of Schottky diodes, photodetectors, and field effect transistors has greatly matured.

Results

Conclusion