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

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%.

Free-carrier absorption in asymmetric double quantum well structures due to static scatterers in the in-plane polarization

“…Thus, the absorption processes can be reliably estimated by the semi-classical description assuming that the carriers are accelerated by the electric force −e F las . As a consequence, the ω −p (p ∼ 2−3) bulk behavior characteristic of the Drude-like approach 16,17 , is recovered in this two-dimensional system for this in-plane polarization configuration.…”

GaAs Blocked-Impurity-Band Detectors for Far-Infrared Astronomy

“…This has important consequences for a BIB detector. As discussed in It has been observed that the compensation ratio, as determined based on the carrier concentration and Hall mobility within the model of Walukiewicz et al [67], is always between 10 and 90% for LPE GaAs films regardless of the majority dopant concentration.…”

“…The free electron concentration of sample 312 as a function of annealing temperature is displayed in Figure 4.6. The Hall mobility and resistivity measured after each anneal is displayed in Table 4.2, along with the compensation ratio determined from [67]. The free electron concentration and other transport properties of the sample saturate at annealing temperatures above 725 • C, with a compensation ratio of between 0.55 and 0.6.…”

“…At 77 K ionized impurity scattering is dominant in n-type GaAs. Walukiewicz et al have calculated the effects of the donor and acceptor concentrations on the electron mobility at room temperature [67] and 77 K [66].…”

Far-infrared absorption in GaAs:Te liquid phase epitaxial films

“…The resulting Te concentrations in the films vary from 1x10 15 cm -3 to 2.1x10 16 cm -3 (Table I). Based on the measured free electron concentration and mobility we estimate the compensation 9 of the films to be between 60-70% for samples 294 and 295, and 80-90% for sample 286.…”