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Photoluminescence (PL) and photoreflectance (PR) were used to characterize ZnxCd1-xSe/MgSe multiple quantum well (MQW) structures grown on InP substrates by molecular beam epitaxy for mid-infrared (IR) device applications. The PL spectra yielded information of the fundamental excitonic recombination and ZnxCd1-xSe cap/spacer band edge emission of the samples. The PR spectra revealed multitude of possible interband transitions in MQW structures. The ground state transitions were assigned by comparing with the PL emission signals taken from the same structures. A comprehensive analysis of the PR spectra led to the identification of various interband transitions. The intersubband transitions were then estimated and found to be in a good agreement with the previous report of Fourier-transform IR absorption measurements [Li et al., Appl. Phys. Lett. 92, 261104 (2008)]. The results demonstrate the potential of using PL and PR as nondestructive optical techniques for characterization of ZnxCd1-xSe/MgSe MQWs for mid-IR device applications. [ABSTRACT FROM AUTHOR]

Highly strained InxGa1-xAs/GaAs double quantum well (DQW) structures grown by metal organic vapor phase epitaxy with different In compositions are investigated by surface photovoltage spectroscopy (SPS) in the temperature range 20–300 K. A lineshape fit of spectral features in the differential surface photovoltage (SPV) spectra determines the transition energies accurately. A comprehensive analysis of the anomalous phenomena appearing in lower temperature SPV spectra enable us to evaluate directly the band lineup of DQW and to remove the ambiguity in the identification of spectral features. The process of separation of carriers within the QW with possible capture by the interface defect traps plays an important role for phase change in SPV signal in the vicinity of light-hole related feature at low temperature. The results demonstrate the considerable diagnostic values of the SPS technique for characterizing these highly strained DQW structures. [ABSTRACT FROM AUTHOR]

We present photoreflectance (PR) and surface photovoltage spectroscopy (SPS) studies of GaAs1-xSbx/GaAs multiple quantum well structures with fundamental transition close to 1.3 μm. These two optical diagnostic tools are powerful supplementary techniques in the investigations of complicated quantum systems. PR gives detailed information about the heavy-holes related transitions, while SPS contains additional information concerning light-holes related ones. The comparison of experimental data and theoretical analysis based on the envelope function approximation, including strain and exciton binding energy, allows us to identify the observed PR and SPS features. The results point to the existence of weak type-I band alignment in samples being studied, and the Sb content dependent of conduction band offset is found to agree well with that reported by Wang et al. [Phys. Rev. B 70, 195339 (2004)]. [ABSTRACT FROM AUTHOR]

The coupling effect between the cavity mode and excitonic states in a GaAs/GaAlAs asymmetric microcavity structure was studied via angle and temperature dependent reflectance and piezoreflectance (PzR) measurements in the angular range 10°<θinc<60° and temperature range 20 K

Studies the temperature dependence of quantized states in a quantum well semiconductor heterostructure. Utilization of piezoreflectance and contactless electroreflectance measurements; Identification of excitonic transitions between the conduction band state and heavy band state; Evaluation of the parameters that describe temperature dependence.

Photoreflectance (PR) was used to study the direct-gap interband transitions in strain-compensated Ge/SiGe multiple quantum well (MQW) structures with Ge-rich SiGe barriers grown by low-energy plasma-enhanced chemical vapor deposition. The PR spectra revealed a wide range of possible optical transitions in the MQW structure. Detailed lineshape fits to the PR spectra and comparison to a theoretical calculation based on the envelope-function approximation with conduction band-offset and stain compensation factor as adjust parameters led to the identification of various interband transitions. The results demonstrated that PR is a powerful technique for nondestructive optical characterization of Ge/SiGe MQW structures. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) of a strain-compensated Ge/Si0.15Ge0.85 multiple-quantum-well (MQW) structure was studied above room temperature, in the range of 300-440 K. Both direct and indirect radiative recombination PL features were observed. The relative intensity of direct to indirect recombination markedly increases with the increase of temperature. The enhancement of PL from direct recombination above RT has been attributed to the thermal excitation of carriers from L-type to Γ-type confined states. This extends the potential applicability of Ge/SiGe MQW as light emitters on a Si-based platform and is favorable for applications in metal-oxide-semiconductor integrated circuits which normally operate above RT. [ABSTRACT FROM AUTHOR]

We present temperature dependent surface photovoltage spectra of GaAs1-xSbx/GaAs multiple quantum well structures. Our previous studies [Sitarek et al., J. Appl. Phys. 105, 123523 (2009)] have identified all features present in the surface photovoltage spectra and showed weak type-I band alignment in the investigated GaAsSb/GaAs system. By analyzing the changes in the relative intensity of features near the energy of fundamental transitions caused by the temperature variations, we are able to determine the energy difference between electronic states localized in GaAsSb quantum well and conduction band edge in the GaAs barrier. In addition, the Bose-Einstein parameters that describe the temperature dependences of 1hh-1e transitions are evaluated and discussed. [ABSTRACT FROM AUTHOR]

Temperature-dependent piezoreilectance (PzR) measurements were used to study the direct-gap-relateil optical transitions in a strain-compensated Ge/SiGe multiple-quantum-well (MQW) structure with Ge-rich SiGe barriers in the temperature range between 20 and 375 K. The PzR spectra revealed a wide range of possible optical transitions in the MQW structure. Detailed line-shape fits to the PzR spectra and comparison to a theoretical calculation based on the envelope-function approximation led to the identification of various interband transitions. In addition, the parameters that describe the temperature dependence of the excitonic transition energies [E(T)] and broadening parameters [&Ggr;(T)] were evaluated and compared to those of the polar systems. In agreement with polar materials, [K(T)] values of the MQW structure were found to be similar to the constituent bulk well material. On the other hand, no significant dimensionality dependence of [&Ggr(T)] was observed, in contrast to polar systems. [ABSTRACT FROM AUTHOR]