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Deep-level defect-related optical properties of undoped n-type GaN grown by metalorganic chemical vapor deposition are investigated using photoluminescence (PL), optical absorption (OA), photoconductivity (PC), and persistent photoconductivity (PPC) measurements. From the temperature dependence of the PL and OA, we find that the yellow luminescence (YL) is due to shallow-to-deep donor recombination. PL, PC, and PPC results manifest a strong correlation in properties related to deep levels. Samples which emit YL exhibit a PC peak at 1.9 eV due to the photoionization of deep levels as well as to the persistent photoconductivity effect, whereas samples with no YL have no PC peak in the forbidden gap and no PPC at any photon energy, suggesting a common origin. Furthermore, two types of PPC behavior were observed depending on the sample quality: typical stretched exponential decay in relatively thick samples and photocurrent quenching and a subsequent reduction of the dark current in thin samples. An explanation of the latter phenomenon based on photoinduced metastable electron traps in a highly defective layer near the interface is suggested from the temporal behavior of the PC. These traps seem to disappear slowly after the illuminating light is turned off. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated the optical properties of AlxGa1-xN/GaN heterostructures (x=0.08, 0.15, 0.33) grown by metal organic chemical vapor deposition on sapphire using photoluminescence (PL) and persistent photoconductivity (PPC) measurements. For the AlxGa1-xN/GaN heterostructures (HS) containing high Al composition, we observed an anomalous temperature-dependent photoluminescence and persistent photoconductivity effects. These results show a strong dependence of the physical properties of AlxGa1-xN/GaN HS on the Al content and layer thickness. The anomalous temperature-dependent PL is usually attributed to the presence of carrier localization states. These phenomena are explained based on the alloy compositional fluctuations in the AlxGa1-xN/GaN HS. From the PPC measurements, the photocurrent (PC) quenching was observed for AlxGa1-xN/GaN HS and it is explained by the metastable states formed in the underlying GaN layer. Also, the mechanisms behind the PC quenching and PPC phenomena are explained in detail. [ABSTRACT FROM AUTHOR]

We present the results of photoluminescence experiments on InSb/AlxIn1-xSb multi-quantum-wells on GaAs substrates. A comparison of the photoluminescence signals with transmission measurements shows Stokes shifts of 2.8–6.9 meV, indicating that the low temperature luminescence is mainly due to bound excitons localized by interfacial potential minima. The high temperature signal is attributed to ionized free carriers. The well width dependent thermal activation energy investigation indicates that nonradiative carrier loss from the wells to the barriers is not a dominant mechanism. Instead, we suggest that the thermal recombination by surface dislocations or defects might be the main nonradiative channel for high temperature luminescence. [ABSTRACT FROM AUTHOR]

InAs/InAs0.865Sb0.135 quantum wells are characterized using magneto-photoluminescence. Band- to-band transitions are found at energies lower than the band gaps of either the InAs or the InAs0.865Sb0.135 with photoluminescence emission at wavelengths up to 4.8 μm. By modeling the quantum size shifts of the photoluminescence transitions and their energy shift in a magnetic field, the valence band offset between InAs and In(As,Sb) is deduced to be type II with electron confinement in the In(As,Sb) alloy and hole confinement in InAs. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]