Investigations on epitaxy and lattice distortion of sputter deposited β-Ga₂O₃ layers on GaN templates

Abstract

The lattice distortion and epitaxial nature of β-Ga2O3 layers deposited on GaN templates using radio-frequency magnetron sputtering have been evaluated. The determined values of out-of-plane (tensile type) and in-plane (compressive type) strain are found to decrease with increase in deposition temperature, indicating better relaxation of the unit cell lattice at higher temperatures. The obtained value of angle β is invariably higher than its bulk value, suggesting a distortion in the unit cell of β-Ga2O3 layer. Columnar-type growth for β-Ga2O3 layer on GaN template has been observed. Analysis of its epitaxial nature reveals that six domains of grown layer are in-plane rotated by 60° ± δo (δ = 2°–3°) with each other, which is explained by the presence of three non-equivalent oxygen atoms on the (−201) plane of β-Ga2O3. The calculated values of δ nearly match experimentally observed values. However, the smaller difference between the two is related to residual strain in the layer. The out-of-plane and in-plane epitaxial relationship for β-Ga2O3 layer with respect to GaN are (−201)Ga2O3 || (0001)GaN and (010)Ga2O3 || (11–20)GaN, respectively.