UP-CONVERTED PHOTOLUMINESCENCE IN ORDERED AlGaInP ALLOY SEMICONDUCTOR SESTEMS AND ITS PRESSURE EFFECTS

点击翻译按钮获取中文摘要

Ga_<0.5>In_<0.5>P grown on GaAs substrates under appropriate conditions is known to form naturally ordered superlattices with the CuPt structure. Although the interface plays an important role in the formation of the ordered structure, little is known about it due to difficulties in probing the heterointerface in as grown samples. We have observed upconversion of photoluminescence (PL) from GaInP at -1.9 eV in several partially ordered GaInP epilayers grown on GaAs and in GaAs/GaInP quantum well structures when the excitation photon energy (1.58 eV) is sufficiently below that of GaInP but is slightly above the bandgap of GaAs near 1.5 eV.While the spectral" positions are almost close to those of the normal PL excited by photons with energy of 2.54 eV, some of their spectral shapes are quite different from those of normal PL spectra. Since this upconversion process occurs in the vicinity of the interface, it can be used to probe properties of the heterojunction such as the band offsets and diffusion of carriers across the interface. A two-photon absorption mechanism at the type II GaAs/partially ordered GaInP interface seems to explain our results. Also, we have studied the time-resolved photoluminescence in GaAs/partially ordered GaInP quantum wells, which is an alternative way of probing the interfaces. Some of these structures contain thin (- 2 nm) layers of GaP between the GaInP and GaAs layers. A so-called "deep emission" band at -1.46 eV is dominated. This deep emission is closely related to the order-disorder phenomenon observed previously for GaInP.A model for spatially indirect recombinations of electron and holes at the interface without GaP layer is proposed to explain our results, in which the conduction band alignment at the GaAs/partially ordered GaInP is of type II.