Stress control by micropits density variation in strained AlGaN/GaN/SiN/AlN/Si(111) heterostructures

Abstract

AlGaN/GaN heterostructures were deposited on Si utilizing in‐situ SiN masking layer as a mean to decrease stress present in the final heterostructures. Structures were grown under different V/III ratio using metalorganic vapour phase epitaxy (MOVPE). Additional approach was applied to obtain crack‐free heterostructures which was deposition of 15 nm low temperature AlN interlayer. Each of the heterostructure contained GaN layer of 2.4 μm total thickness. In‐situ SiN masking layer were obtained via introduction of SiH4 precursor into reactor under high temperature growth conditions for 100 s. In that manner, few monolayers of SixNx masking layer were deposited, which due to the partial coverage of AlN, played role of a mask leading to initial 3D growth mode enhancing longer coalescence of GaN buffer layer. To study surface morphology AFM images were observed. Three methods were used in order to obtain basal plane stress present in multilayer structures ‐ MicroRaman spectroscopy, XRD studies and optical profilometry. It was found that varying V/III precursors ratio during GaN layer growth characteristic for structures with the SiN mask approach formation of triangular micropits can be minimized. Outcomes for three different methods turned out to be coherent. It was found that certain amount of micropits on the surface can be advantageous lowering stress introduced during cooling after process to the AlGaN/GaN/SiN/AlN/Si(111) structure.