Steady-State Electron Transport and Low-Field Mobility of Wurtzite Bulk ZnO and Zn1−x Mg x O

Abstract

Steady-state electron transport and low-field electron mobility characteristics of wurtzite ZnO and Zn1−xMgxO are examined using the ensemble Monte Carlo model. The Monte Carlo calculations are carried out using a three-valley model for the systems under consideration. Acoustic and optical phonon scattering, intervalley (equivalent and nonequivalent) scattering, ionized impurity scattering, and alloy disorder scattering are used in the Monte Carlo simulations. Steady-state electron transport is analyzed, and the population of valleys is also obtained as a function of applied electric field and ionized impurity concentrations. The negative differential mobility phenomena is clearly observed and seems compatible with the occupancy and effective nonparabolicity factors of the valleys in bulk ZnO and in Zn1−xMgxO with low Mg content. The low-field mobilities are obtained as a function of temperature and ionized impurity concentrations from the slope of the linear part of each velocity–field curve. It is seen that mobilities begin to be significantly affected for ionized impurity concentrations above 5 × 1015/cm3. The calculated Monte Carlo simulation results for low-field electron mobilities are found to be consistent with published data.