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Effect of Impurity Compensation on Electron Mobilities in the Multiconduction Bands of GaAs
A. K. Saxena, Sonal Singhal, S. Dasgupta and S. Agarwala

GaAs is one of the most important III-V group compound semiconductors for optical, high field and high frequency homo and hetero structure devices. It is widely used because of its high electron mobility feature and band gap compared to Si. The electron drift mobility in Γ conduction band of GaAs has been calculated before as a function of temperature and compensation ratio but for the first time, we have made attempts to estimate the electron mobilities in higher energy L and X minima. We have also calculated the value of mobility of two dimensional electron gas needed to predict heterostructure device characteristics using GaAs. Ionized impurity, polar mode, deformation potential and piezoelectric scatterings are included in calculations. Best scattering parameters have been derived by close comparison between experimental and theoretical mobility. Room temperature electron mobilities in Γ, L and X valleys are found to be nearly 9094, 945 and 247 cm2/V-Sec respectively. For the above valleys, the electron masses, deformation potentials and polar phonon temperatures have been determined to be (0.067, 0.22, 0.39 m0), (8.5, 9.5, 6.5 eV), and (416, 382, 542 K) respectively. The 2-DEG electron mobility in Γ minimum increases to 1.54 × 106 from 1.59 × 105cm2/V-Sec (for impurity concentration of 1014cm-3) at 10 K. Similarly the 2-DEG electron mobility values in L and X minima and estimated to be 2.28 × 105, 1.44 × 105cm2/V-Sec at 10 K, which are about ~ 4.5 and ~ 3.9, times higher than normal value with impurity scattering present. The effect of impurity compensation on mobility has also been studied.

Keywords: GaAs, Scattering, Mobilities in Γ, L, and X valleys, Effective masses, Deformation potential, Impurity compensation and 2-DEG.

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