Defect Structure and Luminescence of κ‐Ga₂O₃ Micro‐Monocrystals

Abstract

Wide bandgap orthorhombic polymorph of gallium oxide (κ‐Ga2O3) possessing a high spontaneous polarization grown on wurtzite‐type semiconducting substrates is considered to create a high mobility electron channel suitable for applications. Such κ‐Ga2O3 layers are composed of hexagon microprisms whose properties affect the lateral electric conductance. In this work, the structure and recombination properties of extended defects in individual “suspended” thin microprisms are investigated with transmission and scanning electron microscopy techniques (STEM, HR‐TEM) including cathodoluminescence (CL‐SEM). It is established that the microprism is composed of six equisized orthorhombic domains bounded by twin domain boundaries (TDBs) along the directions <110>. Twin domain contains a parallel array of antiphase boundaries (APB) of a high density stretched in the [010] direction. APBs possess steps or interruption and can form double oppositely shifted spatially separated layers (APB dipoles). TDBs on majority of their length are incoherent and serve as the border for the APB terminations. Panchromatic CL maps reveal either enhanced or reduced intensity of APB without noticeable spectral changes. CL intensity enhancement is proposed to be due to enhanced electron–hole generation caused by excess scattering of primary electron beam by APBs in thin films while, in fact, APB exhibits enhanced nonradiative recombination activity.