Scattering analysis of 2DEG carrier extracted by QMSA in undoped Al_(0.25)Ga_(0.75)N / GaN heterostructures

摘要

Hall effect measurements on undoped Al_(0.25)Ga_(0.75)N/GaN heterostructures grown by a metalorganic chemical vapour deposition (MOCVD) technique have been carried out as a function of temperature (20-350 K) and magnetic field (0-1.5 T). Magnetic field dependent Hall data were analysed using the quantitative mobility spectrum analysis (QMSA) technique. The mobility and density within the two-dimensional electron gas (2DEG) at the Al_(0.25)Ga_(0.75)N/GaN interface and within the underlying GaN layer were successfully separated by QMSA. Mobility analysis has been carried out using both the measured Hall data at a single field and the extracted data from QMSA. Analysis of the temperature-dependent mobility of 2DEG extracted from QMSA indicates that the interface roughness and alloy disorder scattering mechanisms are the dominant scattering mechanisms at low temperatures while at high temperatures only polar optical phonon scattering is the dominant mechanism. Al_(0.25)Ga_(0.75)N/GaN interface related parameters such as well width, deformation potential constant and correlation length were also accurately obtained from the fits of the simple analytical expressions of scattering mechanisms to the 2DEG mobility.