Electron mobility and free-carrier absorption in GaAs: Determination of the compensation ratio

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Abstract
Theoretical calculations of electron mobility and free‐carrier absorption in n‐type GaAs at room temperature were carried out taking into consideration all major scattering processes. It was found that satisfactory agreement between theoretical and experimental results on free‐carrier absorption is obtained only when the effect of compensation is quantitatively taken into account. In conjunction with experimental studies it is shown that the electron mobility (for n≳1015 cm−3) and free‐carrier absorption (for n≳1016 cm−3) are sufficiently sensitive to the ionized impurity concentration to provide a reliable means for determining the compensation ratio. Convenient procedures are presented for the determination of the compensation ratio from the free‐carrier absorption coefficient and from the computed values of room‐temperature electron mobility. Values of the compensation ratio obtained by these two procedures are in good agreement provided the carrier‐concentration variations in the material are not appreciably greater than 10%.