LOGARITHMIC APPROXIMATION FOR THE ENERGY-BAND IN NONPARABOLIC SEMICONDUCTORS

We propose a semi-empirical logarithmic approximation to the conductio n band of small gap semiconductors. This approximation enables us to o btain analytical expressions for the intrinsic absorption coefficient and free electron density, and these expressions are valid for a large temperature range. We show that the exponential variation of the abso rption coefficient, as observed by Chu et al. [J. H. Chu et nl., J. Ap pl. Phys. 71, 3955 (1991)] in Hg1-xCdxTe, can be fitted very well for any temperature using only a few parameters whereas the analytical exp ression for free electron density is useful in optical and transport s imulations. (C) 1998 American Institute of Physics.