Deep-level traps in lightly Si-doped n-GaN on free-standing m-oriented GaN substrates

H Yamada,H Chonan,T Yamada,M Shimizu,T Takahashi

doi:10.1063/1.5011362

H Yamada, H Chonan + Show 3 more

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https://doi.org/10.1063/1.5011362

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Abstract

In this study, we investigated the deep-level traps in Si-doped GaN epitaxial layers by metal-organic chemical vapor deposition on c-oriented and m-oriented free-standing GaN substrates. The c-oriented and m-oriented epitaxial layers, grown at a temperature of 1000 °C and V/III ratio of 1000, contained carbon atomic concentrations of 1.7×1016 and 4.0×1015 cm–3, respectively. A hole trap was observed at about 0.89 eV above the valence band maximum by minority carrier transient spectroscopy. The trap concentrations in the c-oriented and m-oriented GaN epitaxial layers were consistent with the carbon atomic concentrations from secondary ion mass spectroscopy and the yellow luminescence intensity at 2.21 eV from photoluminescence. The trap concentrations in the m-oriented GaN epitaxial layers were lower than those in the c-oriented GaN. Two electron traps, 0.24 and 0.61 eV below the conduction band (EC) minimum, were observed in the c-oriented GaN epitaxial layer. In contrast, the m-oriented GaN epitaxial layer was free from the electron trap at EC – 0.24 eV, and the trap concentration at EC – 0.61 eV in the m-oriented GaN epitaxial layer was lower than that in the c-oriented GaN epitaxial layer. The m-oriented GaN epitaxial layer exhibited fewer hole and electron traps compared to the c-oriented GaN epitaxial layers.

Highlights

Gallium nitride (GaN)-based wide bandgap semiconductors have been attracting much attention for optoelectronic applications[1] and high-power and high-frequency transistors.[2]
We recently reported that the carbon residual impurity concentrations in the m-oriented GaN epitaxial layer were more significantly suppressed than those in the c-oriented GaN.[20]
We report the electron and hole traps in the c-oriented and m-oriented GaN epitaxial layers grown by MOCVD

Summary

INTRODUCTION

Gallium nitride (GaN)-based wide bandgap semiconductors have been attracting much attention for optoelectronic applications[1] and high-power and high-frequency transistors.[2]. A state-of-the-art MOCVD growth condition under a high pressure and/or high group-V to III ratio (V/III) enables the reduction of the carbon residual impurity concentration to less than 1×1016 cm–3 for the c-oriented GaN epitaxial layer. We recently reported that the carbon residual impurity concentrations in the m-oriented GaN epitaxial layer were more significantly suppressed than those in the c-oriented GaN.[20] The electrical properties of Ni/nGaN vertical SBDs on the m-oriented GaN substrates demonstrated a low leakage current under a reverse bias owing to low oxygen and carbon residual concentrations. We report the electron and hole traps in the c-oriented and m-oriented GaN epitaxial layers grown by MOCVD. The m-oriented GaN epitaxial layers demonstrated fewer electron and hole traps compared to the c-oriented GaN

EXPERIMENT

Donor and acceptor concentrations in Si-doped n-GaN epitaxial layers

Hole traps in the Si-doped n-GaN epitaxial layers

Electron traps in the Si-doped n-GaN epitaxial layers

CONCLUSIONS