Monte Carlo calculation of two-dimensional electron gas mobility in InN-based heterostructures

We present a theoretical study of the low-field mobility of two-dimensional electron gases (2DEGs) formed in gated In0.05Ga0.95N/InN heterostructures using the ensemble Monte Carlo method. The main emphasis is given to investigate the dependence of the mobility on the electron sheet density which can be effectively controlled by a variation of the gate bias. The major scattering mechanisms such as Coulomb scattering related to the presence of charged threading dislocations and ionized impurities, interface roughness, and phonon scatterings are included in the Monte Carlo calculations. Relative contributions from individual scattering mechanisms to the 2DEG mobility depending on temperature, dislocation concentration, and electron sheet density are discussed. It was found, that charged threading dislocations with concentrations in excess of 10(8) cm(-2) are the major limitation of the two-dimensional electron mobility at low temperatures and low sheet densities of the 2DEG. However, when by a positive gate bias the electron distribution is pushed closer to the interface (high electron sheet density regime), interface roughness scattering becomes the dominant scattering mechanism and the mobility drastically decreases. The room temperature 2DEG mobility, even for an ionized impurity concentration N-imp=10(16) cm(-3), would attain a value as high as 12 500 cm(2)/V s in case if In0.05Ga0.95N/InN heterostructures could be grown without dislocations. For dislocation densities ranging from 10(8) to 10(10) cm(-2), the room temperature electron mobility varies from about 10 000 to 1000 cm(2)/V s, respectively. (c) 2007 American Institute of Physics.