Photoluminescence Visible at 77 K from Indirect-Gap Al_xGa_1-xAs Grown by Organometallic Vapor Phase Epitaxy

Abstract

We have observed two intense photoluminescence bands in the energy range of 1.84 to 1.98 eV for indirect-gap p-type Al x Ga1-x As. They are extraordinarily intense (visible at 77 K) for indirect recombination. Their full-widths at half maximum are relatively broad (30–60 meV). Their peak energies and relative intensities depend on the type of sample used (x, undoped, intentionally C-doped or annealed). Their intensities increase superlinearly with increasing excitation intensity, which is indicative of exciton recombination. These bands are absent for slightly Si-doped n-type materials. The origin of these strong emissions is also discussed.