Luminescence due to Ge Acceptors in GaAs

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Abstract
A study was made of photoluminescence in n‐ and p‐type Ge‐doped GaAs grown by liquid‐phase epitaxy and of electroluminescence of Ge‐compensated diodes. It is shown that two radiative emission bands are observed at 77°K, which are due to acceptor levels at Eν+0.03 eV and Eν+0.07 eV introduced by Ge. The shallow level is attributed to isolated Ge atoms on As sites, while the deeper level is believed to consist of an atomic complex involving Ge. The density of the deeper centers relative to the shallower ones depends on the growth conditions. In the samples studied, the deep center density is 102 to 103 smaller than the shallow center density. A detailed investigation has been made of the density‐of‐states distribution of the deeper acceptor levels and the experimental data have been compared to the theory of Morgan. This model considered the effect of the screened Coulomb potential due to charged impurities on the density‐of‐states distribution of deep recombination centers. The present materials are of particular interest in this respect because the recombination band involving the same set of deep impurity states may be observed in nearly compensated n‐ and p‐type material and the relative effects of screening by either electrons or holes may, in principle, be determined. The experimental results support some of the predictions of Morgan's theory.