We study the dependence of low field mobility on various parameters such as well width and interface roughness for a two-dimensional electron gas confined to a AlGaN/GaN quantum well as a function of temperature. The potential profile, the energy levels, electron concentrations and wave functions for each level are found from the self-consistent numerical solution of Schrödinger and Poisson equations for the quantum well. Then the scattering rates for electrons due to acoustic phonons, optical phonons and interface roughness are obtained using the self consistently calculated wave functions. Ensemble Monte Carlo technique is used to find the drift velocities of the two-dimensional electrons along the interface. The mobility of two-dimensional electrons is extracted from these data. Electron transport properties of bulk GaN is also studied in order to compare the two and three-dimensional mobility values. It is seen that electron mobilities upto 40 × 10 3 cm 2 /Vs can be obtained in a 2DEG confined to an AlGaN/GaN hetero interface. The results of simulation are compared with experimental findings and it is seen that the agreement between simulation and experiments in two dimensions is very satisfactory.
The results of an ensemble Monte Carlo model of the electron transport in wurtzite gallium nitride (GaN) and indium nitride (InN) are presented. There is a controversy over the material parameters of InN, therefore the recently reported and the traditionally accepted parameter values for InN are used in simulations and the results are compared. The steady-state and transient electron transport characteristics are analyzed and the valley populations of electrons are determined as a function of electric field. The low-field mobility of electrons is also obtained as a function of temperature and over a wide range of carrier concentrations. It is seen that with the recently published material parameters the peak velocity of carriers in InN increases significantly, while the field at which it is attained decreases. The calculated maximum low field mobility at 300 K in InN with the recent material parameters is about 10000 cm 2 /V s for low carrier concentrations.
Steady-state electron transport and low-field electron mobility characteristics of wurtzite ZnO and Zn 1Àx Mg x O 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 Zn 1Àx Mg x O 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 9 10 15 /cm 3 . The calculated Monte Carlo simulation results for low-field electron mobilities are found to be consistent with published data.
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