Spatially Variable Drift Mobility Model for Hg1−xCdxTe Diodes I. Analytical Base and Fit to Hall Data

Abstract

A microscopic model of the drift mobility in Hg1−xCdxTe (x ≈ 0.2) is established on the basis of the Kohler variational method. The relevant scattering michanisms, degeneracy, Kane band structure, and structural point defects are included. The dependence of the electron mobility on the Fermi level position is investigated. The model is compared with experimental Hall data taking into account calculated Hall factors. The spatial variability of electron and heavy hole drift mobilities in a 1Dn+n− p‐junction diode is demonstrated. The mobility routine, which can easily be modified for other materials, will be applied in a 2D device simulation package.

Role of Dislocation Scattering on the Electron Mobility of n-Type Long Wave Length Infrared HgCdTe on Silicon

“…For high purity samples, where the extent of compensation is negligible, alloy scattering becomes important at low temperatures, and the maximum in the mobility versus temperature curve disappears and is replaced by a curve that reaches a maximum and then remains unchanged as the temperature is decreased. [6][7][8][9] From the data in Fig. 1, it is evident that the standard 78 K Hall measurement of HgCdTe on bulk CdZnTe is actually a measure of the Hall mobility in the lattice scattering dominated region of the mobility versus temperature curve.…”

“…This is consistent with the Hall mobility data reported and modeled previously for HgCdTe grown on CdZnTe. [5][6][7][8][9][10][11][12][13] It is important to note that the dislocation scattering term in Fig. 5 decreases with temperature.…”

“…[5][6][7][8][9][10][11][12][13] The dominant scattering mechanisms in n-type HgCdTe are ionized impurity scattering (IS), alloy disorder (AD), acoustic phonon (AP) and polar optical (PO) phonon scattering. Interface roughness scattering has been shown to be important in HgTe/CdTe super lattice structures, but it is considered negligible in bulk HgCdTe layers.…”

“…Variational methods such as KohlerÕs method must be employed to eliminate these errors. 6,9 The standard approach to calculating the electron mobility is to calculate as a function of temperature the individual mobilities based on the different scattering mechanisms that are believed to be operating within the materials system and then add the different mobilities using MatthiesenÕs rule…”

“…3,4 However, single field, variable temperature, Hall mobility measurements have typically been used to model the electron mobility of n-type HgCdTe, assuming that a single carrier type (single electron) is dominant. [5][6][7][8][9][10][11] The single electron approximation has been adopted for this analysis of the electron mobility of n-type LWIR HgCdTe on Si.…”