Studies of the Optical Impurity‐Band Transition Using a Single Potential of an Impurity Centre

Abstract

Optical I' impurity-band" transitions have been studied in various models. For example, optical transitions in which shallow impurities take part a r e well described within the frames of a hydrogen-like model /l/. Deep acceptor photodeionization is considered in the delta-function potential model of Lucovsky /2/. Optical transitions involving not too deep and not too shallow impurities are calculated using the Hulten potential /3/.Thus, optical transition problems with shallow donor levels created by group V elements and with deep donor levels created by singly ionized ions of group VT are solved by means of various approaches, though from the physical viewpoint there is no difference between these defects except for the central charge. The same is true for shallow and deep acceptors created by group ITI elements and singly charged group I f ions, respectively. Besides, the above mentioned theories suffer from a serious disadvantage -introduction of a fitting parameter taking into account the increase of the optical transition amplitude due to the fact that the effective local field exceeds the averagemacroscopicfield in the crystal.Tn /4/ we proposed a model in which the impurity centre potential can be presented in the formwhere z* is the effective charge of the impurity centre which is estimated according to the Slater rules. Since this z* corresponds to the free atom ionization energy differing sufficiently from its experimental value, we make a correction to the Slater rules, so that z* found with allowance for this correction 1) Prospekt Chavchavadze 1, 380028 Tbilisi, USSR.