Discovery of New Photoluminescence Effect Related to Deep Donor Levels in Si-Doped Al_xGa_1-xAs and Microstructures

Abstract

We have discovered a new type of photoluminescence (PL) effect in Si-doped Al_xGa_1-xAs and their microstructures including double δ -doped systems and superlattices. This PL appears with photon energies higher than the incident photon energy at low temperatures. Specifically, the photoexcitation with the energy being 0.2, eV below the gap energy produces the band-edge PL for Al_xGa_1-xAs (0.35≤ x≤ 0.40). Neither the Anti-Stokes Raman effect, the Franz-Keldish effect nor the multiple photon effect have been proven to cause the present anomalous phenomena. Various studies of this luminescence as functions of temperature, Si concentration, the excitation power intensity and the excitation energy have revealed that this effect is strongly related to the deep donor levels in Al_xGa_1-xAs (x≥ 0.3). We have discussed a possible origin of this new phenomena.