DEEP TRAPS SPECTRA IN UNDOPED GAN FILMS GROWN BY HYDRIDE VAPOR PHASE EPITAXY UNDER VARIOUS CONDITIONS

Y N Makarov,E B Yakimov,N B Smirnov,A Y Polyakov,A V Govorkov,H Cox,A S Usikov,H Helava,I H Lee

doi:10.3844/ajassp.2014.1714.1721

Abstract

Decreasing the residual donors density and deep tra ps spectra densities in undoped GaN films grown by Hydride Vapor Phase Epitaxy (HVPE) is very important for promoting the use of such material in highvoltage/high-power rectifiers, radiation detectors. In this study we studied the effects of changing t he growth temperature of undoped HVPE GaN films on these properties. The two groups of undoped GaN HVPE samples analyzed in this study were grown at growth temperature being either 850oC or 950oC. Measurements by means of Capacitance-Voltage (C-V) profiling, deep levels transient spectroscopy, Micr o Cathode Luminescence (MCL) spectroscopy and imaging and by Electron Beam Induced Current (EBIC) showed a much lower density of residual donors (by almost two orders of magnitude), of deep electron t raps and hole traps (by about an order of magnitude) and considerably (about 1.5 times) longer diffusion le ngth of charge carriers in the films grown at 850oC comp ared to samples prepared at 950oC. The data obtaine d indicate that there is an optimal reduced growth te mperature (close to 850oC) resulting in lower concentration of shallow donors and deep traps whil e still preserving the high crystalline quality of the layer. This is of paramount importance for device a pplications of HVPE grown undoped GaN films.

Highlights

Yoshida et al, 2008) The technique is quite versatile allowing to grow films and crystals of n-typeHydride vapor phase epitaxy is a well-established, p-type and growth technique for fabrication of Group III-Nitrides semi-insulating (Richter et al, 2013; Usikov et al, quality (Liu et al, 2014; Wu et al, 2013; Sato et al, 2008; Lipski, 2010; Reshchikov et al, 2011)
In this study we studied the effects of changing the growth temperature of undoped Hydride Vapor Phase Epitaxy (HVPE) GaN films on these properties
HVPE GaN films and device structures can be very useful for light emitting diodes, high-power rectifiers, transistors and radiation detectors (Dmitriev and Usikov, 2006; Reed et al, 2009; Kurin et al, 2013; Wang et al, 2011; Pearton et al, 2013) present day HVPE films still suffer from a rather high residual donor concentration and relatively high density of deep electron and, hole traps (Lee et al, 2012; Polyakov et al, 2011; Fujito et al, 2009; Yoshida et al, 2008), which seriously limits their applications in device structures

Summary

Introduction

Hydride vapor phase epitaxy is a well-established (typically, by Si doping), p-type (by Mg doping) and growth technique for fabrication of Group III-Nitrides semi-insulating (by deep levels Fe or Zn thick films and bulk crystals with good crystalline compensation) (Richter et al, 2013; Usikov et al, quality (Liu et al, 2014; Wu et al, 2013; Sato et al, 2008; Lipski, 2010; Reshchikov et al, 2011). The dislocation density can be made as low as 104-107 cm−2, depending on the layers thickness (Fujito et al, 2009; Sato et al, 2013) All this makes HVPE a very promising technique for fabrication of bulk GaN that can be used as substrates in nitrides epitaxy. In what follows we analyze how the growth conditions (growth temperature especially) affect the electrical and optical properties and the deep traps spectra of HVPE layers

Methods

Results

Conclusion