Pseudomorphic growth of Si-doped α-(AlGa)2O3 on m-plane α-Al2O3 substrates by molecular beam epitaxy

Abstract

Abstract α-(AlGa)2O3 is an attractive material for high-power devices and vacuum UV optoelectronics. However, α-(AlGa)2O3 on sapphire substrates suffers from lattice relaxation and phase transformation. Here, we investigated the effect of controlling the Al composition and thickness of Si-doped α-(AlGa)2O3 layers pseudomorphically grown on α-Al2O3 (10 1 ¯ 0) substrates by MBE. We found that the critical layer thicknesses of α-(AlGa)2O3 layers with Al compositions of 58%, 66%, and 79% were around 13, 18, and 44 nm, respectively. We also found that a 9.0 nm thick α-(Al0.65Ga0.35)2O3/3.5 nm thick Al2O3 multilayer with 20 periods grew almost pseudomorphically and formed α-(Al0.90Ga0.10)2O3 alloy after post-thermal annealing at 1400 °C.