Photoluminescence spectrum of p-type AlxGa1−xAs:Ge

Abstract

The results of photoluminescence measurements of p-type AlxGa1−xAs:Ge (with 0.03<x<0.39) grown by liquid phase epitaxy are presented. An investigation of the composition and temperature dependencies of the acceptor-related peak in this range shows that Ge behaves as a shallow effective mass-like center. The discontinuity in the variation in peak energy versus composition that occurs at x = 0.30 is explained rather in terms of a crossing of donor levels associated with the direct and indirect band gaps. It is also shown that the luminescence is characteristic of donor-acceptor recombination involving shallow donors for x<0.30, whereas a deep donor or a vacancy complex is indicated for x≳0.30. The broad emission band at ∼1.5 eV has also been investigated but its source has not been identified. The presence of this band in the room temperature spectrum and the implications for characterization of light-emitting devices are discussed.