Defects in m-plane GaN layers grown on (100) γ-LiAlO₂

Abstract

In the last years (100) γ-LiAlO₂ was used as an alternative substrate for GaN epitaxy [1, 2]. In contrast to the commonly used commercial substrates (100)LiAlO₂ allows a nearly lattice-matched growth of both polar c-plane and non-polar m-plane oriented GaN layers. The m-plane oriented GaN layers show absence of internal polarisation fields along the growth direction [1–1.0]GaN which is advantageous for fabrication of optoelectronic devices with high performance [2]. Furthermore, LiAlO₂ decomposition at elevated substrate temperatures [3] leads to spontaneous separation of the substrate from thick GaN layers during post-growth cooling down [1, 4]. This allows the preparation of freestanding GaN layers, which can be used as substrates for subsequent GaN homoepitaxy.