Investigations on epitaxy and lattice distortion of sputter deposited β-Ga<sub>2</sub>O<sub>3</sub> layers on GaN templates
Sahadeb Ghosh, Himanshu Srivastava, P. N. Rao, Mangla Nand, Pragya Tiwari, Arvind K. Srivastava, S. N. Jha, S. K., S. D. Singh, Tapas Ganguli
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.