10.1007/s11446-008-3001-8

Abstract

115As known [1,2], doped compensated semiconductors (in which the concentration of free charge carriers is small compared to the concentration of ionized impurities) exhibit smooth, large-scale fluctuations of random potential with certain characteristic amplitudes ( γ ). The role of this chaotic potential increases with decreasing temperature, while at a fixed temperature it grows under the action of pressure as the free carrier concentration decreases [3]. It is important to develop a method for evaluating the effect of the chaotic potential on the energy spectrum of charge carriers and to assess the correctness of relations obtained for defect-free crystals so as to provide a quantitative analysis of experimental data in each particular case.It should be noted that the pressure coefficients of the energy gaps in semiconductors are virtually pressure-independent at not very high pressures. Moreover, the pressure-induced changes of the deepest minima ε Γ , ε L , and ε X in the conduction bands of various semiconductors (IV, II-VI, III-V, IV-VI, and II-IV-V 2 ) are also approximately the same [4][5][6][7][8]. Previously, the pressure coefficients of the ε Γ , ε L , and ε X extrema relative to the values in absolute vacuum were determined [5] based on a concept according to which the energy of deep strongly localized states in some semiconductors is independent of the uniform (hydrostatic) pressure.For the so-called quasi-gapless semiconductors [6] such as doped compensated p -CdSnAs 2 〈 Cu 〉 [7] (Fig. 1) and p -InAs with an excess acceptor concentration of N ext < 10 17 cm -3 [8], in which a deep impurity band is situated near the edge of the intrinsic band, it was concluded that the law of dispersion established for the ideal semiconductor is valid in semiconductors with a random potential as long as the dependence of energy gaps on the hydrostatic pressure, ∆ε ( P ) , is close to linear. On the other hand, a deviation of the ∆ε ( P ) function from linearity, which increases with a decrease in the temperature and the free carrier concentration, is evidence for a significant influence of the random potential on the dispersion law.Let us consider in more detail the situation in the aforementioned p -CdSnAs 2 〈 Cu 〉 crystals, where a deep PHYSICS