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

Electrical properties of AlGaN/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 degrees-off vicinal substrates are superior to those grown on the 0.5 degrees-off vicinal substrates. Anisotropic phenomenon of the 2DEG mobility in the heterostructures grown on 2.0 degrees-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. (c) 2006 American Institute of Physics.