20-22 May 2015
Asia/Bangkok timezone
The Centennial Celebration of General Relativity Theory and 80 Years of Thai Physics Graduate

Strain modification of MOVPE grown cubic GaN on GaAs (001) with GaN/AlGaN multi-interface buffer layer

21 May 2015, 13:00
3h 30m
Board: MNA-69
Poster presentation Material Physics, Nanoscale Physics and Nanotechnology Poster-3

Speaker

Mr Kunpot Mopoung (Nanoscience and technology, Graduate school, Chulalongkorn University, Bangkok, THAILAND 10330)

Description

We have investigated cubic GaN (c-GaN) layers on GaAs (001) substrates by using high resolution X-ray diffraction (HRXRD) to verify strain modification due to a use of the GaN/AlGaN multi-interface buffer layer. To examine lattice parameters and residual strain, both a symmetric (002) and an asymmetric (113) reflections were performed using 2θ-ω mode HRXRD for different types of c-GaN samples. Cross-sectional scanning electron microscopy (SEM) images were used to verily thicknesses of the buffer layer and the GaN top layers. It is found that the fully relaxed lattice constant of c-GaN was determined to be closer to the values of a hypothetical perfect crystal (4.503 Å). Besides, a type of buffer layers remarkably effects on an in-plane strain (ε$_{\textrm{//}}$), which is caused by a combination of a large lattice-mismatch and a difference of thermal expansion coefficients between GaAs and c-GaN. The c-GaN layers with the AlGaN/GaN structure exhibited a tensile strain. While, the c-GaN layers on the conventional low-temperature grown c-GaN buffer layer were examined to be under compressive strain. With the use of GaN/AlGaN as a buffer layer, residual strain in c-GaN thick layers were adjusted to be a tensile strain. Based on our results, we interpreted this strain modification as a competition between the lattice-mismatch and thermal mismatch stresses. This indicates that the relief of strains in the c-GaN layers has a complicated dependence on a type of buffer layers, especially for multi-interface buffer layer.

Primary author

Mr Kunpot Mopoung (Nanoscience and technology, Graduate school, Chulalongkorn University, Bangkok, THAILAND 10330)

Co-authors

Prof. Kentaro Onabe (Department of Advanced Materials Science, The University of Tokyo, Kashiwa, 
Chiba) Mr Manop Tirarattanasompot (Scientific and Technological Research Equipment Centre, Chulalongkorn University, Bangkok, THAILAND 10330) Mr Nattawut Tanyacasat (Department of Physics, Faculty of Science, Chulalongkorn University) Prof. Sakuntam Sanorpim (Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, THAILAND 10330)

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