Electrical properties of AlGaN/GaN heterostructures grown on vicinal sapphire (0001) substrates by molecular beam epitaxy

摘要

Electrical properties of AIGaN/GaN heterostructures grown on vicinal sapphire (0001) substrates by molecular beam epitaxy (MBE) are investigated. It is found that electrical properties of the two-dimensional electron gas (2DEG) in the heterostructures grown on 2.0°-off vicinal substrates are superior to those grown on the 0.5°-off vicinal substrates. Anisotropic phenomenon of the 2DEG mobility in the heterostructures grown on 2.0°-off substrates is demonstrated, which strongly relates to the macrostep structures on the surface. The 2DEG mobility as high as 2018 cm~2/V s is obtained at the room temperature from the authors' all-MBE-grown sample measured in the direction parallel to the macrostep. It is suggested that the direction effect should be taken into account when designing the device structure.