Towards High‐Mobility Heteroepitaxial β‐Ga₂O₃ on Sapphire − Dependence on The Substrate Off‐Axis Angle

Abstract

This paper presents the heteroepitaxial growth of β‐Ga 2 O 3 thin films on off‐axis (0001) c‐sapphire substrates by low pressure chemical vapor deposition (LPCVD). (−201) oriented β‐Ga 2 O 3 thin films are grown using high purity metallic gallium (Ga) and oxygen (O 2 ) as the precursors. N‐type conductivity in silicon doped β‐Ga 2 O 3 thin films is demonstrated. It is found that the film crystalline quality, surface morphology, and electrical conductivity are remarkably sensitive to the off‐axis angles. X‐ray phi‐scan measurements of the β‐Ga 2 O 3 film grown on on‐axis c‐sapphire indicate the presence of six in‐plane rotational domains due to the substrate symmetry. With the increase of off‐axis angle toward <11–20> of sapphire, one of the in‐plane orientations is strongly favored. The use of off‐axis substrate also reduced the X‐ray rocking curve full width at half maximum and increased the intensities of the Raman peaks. The best electrical properties of the β‐Ga 2 O 3 film are exhibited by the film grown on 6° off‐axis c‐sapphire. The room temperature electron Hall mobility was 106.6 cm 2 V −1 s −1 with an n‐type carrier concentration of 4.83 × 10 17 cm −3 . The results from this study demonstrate high electrical quality β‐Ga 2 O 3 thin films grown on off‐axis c‐sapphire substrates, which are promising for high power electronic and short wavelength optoelectronic device applications.