Study of Nonradiative Recombination Centers in n-GaN Grown on LT-GaN and AlN Buffer Layer by Below-Gap Excitation

M D Haque,N Kamata,M Julkarnain,A Z M Touhidul Islam

doi:10.4236/ampc.2018.83010

M D Haque, N Kamata + Show 2 more

Open Access

https://doi.org/10.4236/ampc.2018.83010

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Abstract

Nonradiative recombination (NRR) centers in n-type GaN samples grown by MOCVD technique on a LT-GaN buffer layer and aAlN buffer layer have been studied by two wavelength excited photoluminescence (TWEPL). The near band-edge photoluminescence (PL) intensity decreases due to the superposition of below-gap excitation (BGE) light of energies 0.93, 1.17 and 1.27 eV over above-gap excitation (AGE) light of energy 4.66 eV. The decrease in PL intensity due to the addition of the BGE has been explained by a two levels recombination model based on SRH statistics. It indicates the presence of a pair of NRR centers in both samples, which are activated by the BGE. The degree of quenching in PL intensity for the sample grown on LT-GaN buffer layer is stronger than the sample grown on AlN buffer layer for all BGE sources. This result implies that the use of the AlN buffer layer is more effective for reducing the NRR centers in n-GaN layers than the LT-GaN buffer layer. The dependence of PL quenching on the AGE density, the BGE density and temperature has been also investigated. The NRR parameters have been quantitatively determined by solving rate equations and fitting the simulated results with the experimental data.

Highlights

Gallium nitride (GaN) has been developed as a basis semiconductor for InGaN and AlGaN ternary compounds for such applications as green, blue, up to deep ultra-violet light emitters and high power electronic devices [1]
Nonradiative recombination (NRR) centers in n-type GaN samples grown by metal organic chemical vapor deposition (MOCVD) technique on a LT-GaN buffer layer and aAlN buffer layer have been studied by two wavelength excited photoluminescence (TWEPL)
Defect States acting as NRR centers in n-type GaN layers grown on a LT-GaN buffer layer and aAlN buffer layer have been studied by TWEPL method

Summary

Introduction

Gallium nitride (GaN) has been developed as a basis semiconductor for InGaN and AlGaN ternary compounds for such applications as green, blue, up to deep ultra-violet light emitters and high power electronic devices [1]. The sapphire substrates are generally used owing to low cost and high temperature stability [3] They introduce threading dislocations in a typical range of 109 - 1011 cm−2 due to lattice and thermal mismatch between epitaxial layer and substrate [4] [5] [6]. High density of these structural defects forms below-gap states in group III-V semiconductors (such as GaAs, InP and GaN) which act as non-radiative recombination (NRR) centers in the crystal and degrade the device efficiency and lifetime [7] [8] [9]. The NRR parameters have been evaluated by systematically solving the rate equations and fitting the results with experimental data

Sample Structure

Measurement

PL Intensity Comparison

TWEPL Measurement

Rate Equation Analysis

Conclusion