Si doping in MOCVD grown (010) β-(AlxGa1−x)2O3 thin films

Abstract

In this work, the structural and electrical properties of metalorganic chemical vapor deposited Si-doped β-(AlxGa1−x)2O3 thin films grown on (010) β-Ga2O3 substrates are investigated as a function of Al composition. The room temperature Hall mobility of 101 cm2/V s and low temperature peak mobility (T = 65 K) of 1157 cm2/V s at carrier concentrations of 6.56 × 1017 and 2.30 × 1017 cm−3 are measured from 6% Al composition samples, respectively. The quantitative secondary ion mass spectroscopy (SIMS) characterization reveals a strong dependence of Si and other unintentional impurities, such as C, H, and Cl concentrations in β-(AlxGa1−x)2O3 thin films, with different Al compositions. Higher Al compositions in β-(AlxGa1−x)2O3 result in lower net carrier concentrations due to the reduction of Si incorporation efficiency and the increase of C and H impurity levels that act as compensating acceptors in β-(AlxGa1−x)2O3 films. Lowering the growth chamber pressure reduces Si concentrations in β-(AlxGa1−x)2O3 films due to the increase of Al compositions as evidenced by comprehensive SIMS and Hall characterizations. Due to the increase of lattice mismatch between the epifilm and substrate, higher Al compositions lead to cracking in β-(AlxGa1−x)2O3 films grown on β-Ga2O3 substrates. The (100) cleavage plane is identified as a major cracking plane limiting the growth of high-quality Si-doped (010) β-(AlxGa1−x)2O3 films beyond the critical thicknesses, which leads to highly anisotropic and inhomogeneous behaviors in terms of conductivity.