Photoionization of short-range acceptor states in uniaxially deformed semiconductors

The photoionization cross section (the absorption coefficient) of holes whi ch are localized on deep centers with a short-range potential and make tran sitions into the valence band of a uniaxially deformed Ge-type semiconducto r is calculated. As a result of the fact that the acceptor level and the ex tremum of the hole subbands split the photoionization threshold also splits , and four types of transitions of this kind arise. The population of the s plit impurity states and the contributions of transitions of each type to t he absorption coefficient change with increasing temperature. Since deforma tion destroys the spherical symmetry of the problem, an appreciable polariz ation dependence of the absorption coefficient appears. The calculation is based on a general quantum-mechanical formula with a transition matrix elem ent employing the wave function of an impurity center accompanying deformat ion. (C) 1999 American Institute of Physics. [S1063-7826(99)01406-4].