Studies of Defect Structure in Epitaxial AlN/GaN Films Grown on (111) 3C-SiC.

Andreea Serban,Vladimir Ene,Doru Dinescu,Nikolay Djourelov,Bogdan Vasile,Victor Leca,Iulia Zai

doi:10.3390/nano11051299

Abstract

Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heterostructure, the consistency of the interfaces, and elemental diffusion are achieved by High Resolution Transmission Electron Microscopy (HR-TEM). In addition, the dislocation densities together with the defect correlation lengths are investigated via High-Resolution X-ray Diffraction (HR-XRD) and the characteristic positron diffusion length is achieved by Doppler Broadening Spectroscopy (DBS). Moreover, a comparative analysis with our previous work (i.e., GaN/AlN/Si and GaN/AlN/Al2O3) has been carried out. Within the epitaxial GaN layer defined by the relationship (111) 3C-SiC || (0002) AlN || (0002) GaN, the total dislocation density has been assessed as being 1.47 × 1010 cm−2. Compared with previously investigated heterostructures (on Si and Al2O3 substrates), the obtained dislocation correlation lengths (Le = 171 nm and Ls =288 nm) and the mean distance between two dislocations (rd = 82 nm) are higher. This reveals an improved crystal quality of the GaN with SiC as a growth template. In addition, the DBS measurements upheld the aforementioned results with a higher effective positron diffusion length = 75 ± 20 nm for the GaN layer.

Highlights

Gallium nitride (GaN) is an important wide band-gap semiconductor used in the fabrication of nitride based heterostructure devices for photodetectors [1], electronics [2,3], and light emitting diodes [4,5] and is considered as a perspective material for positron moderation [6,7]
We report an analysis of the crystal quality of commercially available GaN epitaxial thin film grown on (111) 3C-SiC with an intermediate alsolayer measminum nitride (AlN) buffer layer
The GaN/SiC sample used in this work with dimensions of 10 × 10 × 0.35 mm3 was produced at the NTT Advanced Technology Corporation (Kanagawa, Japan) for highelectron-mobility transistors

Summary

Introduction

Gallium nitride (GaN) is an important wide band-gap semiconductor used in the fabrication of nitride based heterostructure devices for photodetectors [1], electronics [2,3], and light emitting diodes [4,5] and is considered as a perspective material for positron moderation [6,7]. In this sense, understanding GaN’s defect structure becomes vital since any impurities, vacancy defects, or strains can influence its unique physical and optical characteristics [3,5,8]. Si is used as a promising high-quality and low-cost substrate, it still presents a large lattice mismatch

Methods

Results

Conclusion