High optical and structural quality of GaN epilayers grown on (2¯01) β-Ga2O3

Abstract

Producing highly efficient GaN-based optoelectronic devices has been a challenge for a long time due to the large lattice mismatch between III-nitride materials and the most common substrates, which causes a high density of threading dislocations. Therefore, it is essential to obtain alternative substrates with small lattice mismatches, appropriate structural, thermal and electrical properties, and a competitive price. Our results show that (2¯01) oriented β-Ga2O3 has the potential to be used as a transparent and conductive substrate for GaN-growth. Photoluminescence spectra of thick GaN layers grown on (2¯01) oriented β-Ga2O3 are found to be dominated by intense bandedge emission. Atomic force microscopy studies show a modest threading dislocation density of ∼108 cm−2. X-ray diffraction studies show the high quality of the single-phase wurtzite GaN thin film on (2¯01) β-Ga2O3 with in-plane epitaxial orientation relationships between the β-Ga2O3 and the GaN thin film defined by (010) β-Ga2O3 || (112¯0) GaN and (2¯01) β-Ga2O3 || (0001) GaN leading to a lattice mismatch of ∼4.7%. Complementary Raman spectroscopy indicates that the quality of the GaN epilayer is high.