HOLE SCATTERING MECHANISMS IN HG1-XCDXTE

In this paper, we analyze and discuss the roles of nine different scat tering mechanisms - ionized impurity, polar and nonpolar optical, acou stic, dislocation, strain field, alloy disorder, neutral impurity, and piezoelectric - in limiting the hole mobilities in p-type Hg1-xCdxTe crystals. The analysis is based on obtaining a good fit between theory and experiment for the light and heavy hole drift mobilities by optim izing certain unknown (or at the most vaguely known) material paramete rs such as the heavy hole mobility effective mass, degree of compensat ion, and the dislocation and strain field scattering strengths. For th eoretical calculations, we have adopted the relaxation time approach, keeping in view its inadequacy for the polar scattering. The energy di spersive hole relaxation times have been drawn from the published lite rature that take into account the p-symmetry of valence band wave func tions. The temperature dependencies of multiple charge states of impur ities and of Debye screening length have been taken into account throu gh a numerical calculation for the Fermi energy. Mobility data for the present analysis have been selected from the HgCdTe literature to rep resent a wide range of material characteristics (x = 0.2-0.4, p = 3 x 10(15)-1 X 10(17) Cm-3 at 77K, mu(peak) congruent to 200-1000 cm(2) V- 1 s(-1)). While analyzing the light hole mobility, the acoustic deform ation and neutral impurity potentials were also treated as adjustable. We conclude that the heavy hole mobility is largely governed by the i onized impurity scattering, unless the strain field or dislocation sca ttering below 50K, or the polar scattering above 200K, become dominant ; the light hole mobility is mainly governed by the acoustic phonon sc attering, except at temperatures below 30K where the neutral impurity, strain field and dislocation scattering also become significant; the intervalence scattering transitions make negligible impact on the heav y hole mobility, but virtually limit the light hole mobility; the allo y disorder scattering does not dominate in any temperature region, alt hough it exercises some influence at intermediate temperatures; the he avy hole mobility effective mass ratio m(hh)/m(o) congruent to 0.28-0. 33 for crystals with x < 0.4; and the light hole band deformation pote ntial constant is similar to 12 eV.