Carrier Transfer of Deep-Level Localized States in Type-II In_xGa_1−xAs/GaN_yAs_1−y Short-Period Superlattice

Optical properties of InGaAs/GaNAs superlattice are investigated by the photoluminescence and reflectance measurements. A quantum well (QW) emission P_M (centered at ≈1.2 eV) and a broad low-energy emission (LEE) band, which can be resolved to three peaks P_A′, P_A, and P_B (0.77, 0.83, and 0.92 eV) are observed. The peak positions of the LEE exhibit S-shaped behavior, whereas the QW emission shows a red shift with increasing temperature. The LEE bands are attributed to N-related deep-level localized state. The photoluminescence (PL) peak of QW exhibits a significant blue shift and saturation effect with increasing excitation density, which is interpreted in terms of the band-bending model in the InGaAs/GaNAs short-period superlattice (SPSL) with a type II band alignment. Furthermore, carrier transfer among these N-related localized states is elucidated by examining the temperature-dependent photoluminescence. Such carrier transfer is also demonstrated by the thermal effect under high excitation density.