Abstract
Photoluminescence (PL) is a nondestructive and powerful method to investigate carrier recombination and transport characteristics in semiconductor materials. In this study, the temperature dependences of photoluminescence of GaAs-AlxGa1-xAs multi-quantum wells samples with and without p-n junction were measured under both resonant and non-resonant excitation modes. An obvious increase of photoluminescence(PL) intensity as the rising of temperature in low temperature range (T < 50 K), is observed only for GaAs-AlxGa1-xAs quantum wells sample with p-n junction under non-resonant excitation. The origin of the anomalous increase of integrated PL intensity proved to be associated with the enhancement of carrier drifting because of the increase of carrier mobility in the temperature range from 15 K to 100 K. For non-resonant excitation, carriers supplied from the barriers will influence the temperature dependence of integrated PL intensity of quantum wells, which makes the traditional methods to acquire photoluminescence characters from the temperature dependence of integrated PL intensity unavailable. For resonant excitation, carriers are generated only in the wells and the temperature dependence of integrated PL intensity is very suitable to analysis the photoluminescence characters of quantum wells.
Highlights
Quantum wells can be grown either by molecular-beam epitaxy (MBE ) or by metal-organic chemical vapour deposition[21,22], because of the low lattice mismatch between AlAs and GaAs
The temperature dependence of integrated PL intensity measured under non-resonant excitation reflects the combination effects of carrier transport from barriers to wells and carriers recombination in the wells, which can not be used to analysis the non-radiative mechanism in the quantum wells by the traditional Arrhenius plot
The activation energies of PL thermal quenching at high temperature fitted by the modified Arrhenius formula are compare to the barrier height for the exciton escaping out of well, which confirms that the non-radiative channel at high temperature is related to the non-radiative centers in barriers
Summary
Quantum wells can be grown either by molecular-beam epitaxy (MBE ) or by metal-organic chemical vapour deposition[21,22], because of the low lattice mismatch between AlAs and GaAs. Due to the above advantages of GaAs/AlGaAs quantum wells, the specific roles of drifting and diffusion played in the PL process under non-resonant excitation can be distinguished in this structure. The GaAs/AlGaAs multi-quantum well structure is used to clarify the specific origin of the abnormal increase of PL intensity and the application range of different excitation modes. For PL measured under resonant excitation, carriers are generated only in the wells and the temperature-dependent integrated PL intensity can reflect the characters of nonradiative channel in the GaAs wells. The specific origin of the anomalous temperature dependence of photoluminescence is clarified and nonradiative characters of GaAs quantum wells are investigated using a modified Arrhenius equation under resonant excitation
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