The Cathodoluminescence of Cr-Doped GaAs Prepared by MOCVD Epitaxy
The cathodoluminescence of p-type, n-type and SI epitaxial layers of Cr-doped GaAs has been studied in the temperature range 10–300 K. Four luminescence bands have been detected which are associated with the presence of chromium in the crystals. Correlation with deep level assessments on similar MOCVD material undertaken by other workers in collaboration with this research, has indicated that two of the bands are due to radiative hole capture at defined deep level states. Band A with threshold near 1.2 eV (10 K) is associated with a state which may be the Cr substitutional acceptor occupied by two electrons (Cr1+). The band with threshold near 0.8 eV (10 K) is associated with recombination at the better established, single electron occupied (Cr2+) substitutional acceptor which is considered to be a dominant Cr species, controlling the electrical properties of the crystals. The latter assignment is successfully tested by comparing the temperature dependence of the luminescence and photocapacitance thresholds. A third band, band D, with threshold also near 1.2 eV is associated with the formation of the neutral (Cr3+) state of the same centre by electron capture from the conduction band. The occurrence of two of the luminescence bands is in substantial agreement with results obtained by other workers on similarly counter-doped, ingot materials.
KeywordsLuminescence Band Epitaxial Material Ingot Material Radiative Electron Capture Deep Level State
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