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We report a detailed investigation on the optical transitions of strained type II GaAs[SUB0.7]Sb[SUB0.3]/GaAs (100) multiple quantum wells. For the theoretical calculations, both of the elastic deformational potential of intrinsic compressive biaxial strain, and quantum confinement effects are included. The asymmetric photoluminescence spectra reveal the features of excited state transition and quantum confinement Stark effect at high and low temperatures, respectively. The asymmetry features have also been investigated and confirmed by low-temperature photoluminescence experiments under different excitation power. From polarized photoluminescence excitation and photoconductivity spectra, both of the type I and type II optical transitions can also be clearly identified. [ABSTRACT FROM AUTHOR]

Detailed studies are reported on the photoluminescence of InAsSb/InAs multiple quantum wells grown by molecular beam epitaxy on InAs substrates with the Sb mole fraction ranging from 0.06 to 0.13. From 4 K photoluminescence the band alignment was determined to be staggered type II. By comparing the emission peak energies with a transition energy calculation it was found that both the conduction and valence bands of InAsSb alloy exhibit some bowing. The bowing parameters were determined to be in the ratio of 4:6. For a sample with Sb composition ∼0.12 in the quantum well the photoluminescence emission band covers the CO2 absorption peak making it suitable for use in sources for CO2 detection. [ABSTRACT FROM AUTHOR]

Investigates the thermal relaxation of the photoluminescence (PL) in InAs/GaAs quantum dot superlattices having two to more than three times the critical thickness for spontaneous island formation. Role of repopulation in the PL quenching; Attribution of the temperature dependence of PL energy to the dilation of lattice and electron-lattice interaction.

We report molecular beam epitaxial growth and characterization of dilute nitride InAsN:Sb. X-ray diffraction, energy dispersive x-ray spectrometry, and electron probe microanalysis revealed that nitrogen incorporation is significantly enhanced by introduction of Sb flux during growth, together with a dramatic improvement of the photoluminescence. These observations were attributed to the surfactant effect of Sb which suppresses the surface diffusion length of nitrogen and improves the homogeneity of the alloy. Sb incorporation is enhanced with the presence of nitrogen which was associated with the surface kinetic of growth. InAsN:Sb/InAs p-i-n light emitting diodes operating near 4.0 μm were also realized. [ABSTRACT FROM AUTHOR]

The authors report on midinfrared photoreflectance measurements of the band gap (E0) and spin-orbit splitting energies (Δ0) in InAs-rich InAsSb and GaInAsPSb samples for varying antimony contents ≤22.5%. The E0 behavior as a function of Sb content is consistent with the literature value bowing parameter of ∼670 meV. However, Δ0 does not exhibit the positive bowing of +1170 meV quoted in the literature: rather, a best fit to their data tentatively suggests a negative bowing of -225 meV. This result is likely to have strong impact due to the importance of the Δ0 parameter in governing InAsSb-based device performance [ABSTRACT FROM AUTHOR]

We report the temperature-dependent photoluminescence characterization of InNxAs1-x/In0.53Ga0.47As/InP multiple quantum wells with various N contents emitting in the midinfrared wavelength range. The emission wavelength in this material system can be tuned by the N content, but the bowing effect is much weaker than in GaNAs. The correlation between the optical properties and the interface quality is demonstrated by examining the barrier-related emission. The role played by N is elucidated by comparing quantum well samples having either zero, low (0.25%) or high (5%) N content. [ABSTRACT FROM AUTHOR]

The optoelectronic properties of undoped type-II GaAs0.7Sb0.3/GaAs (100) multiple quantum wells have been investigated by photoluminescence (PL), and photoconductivity measurements. Quite interestingly, persistent photoconductivity (PPC) has been discovered in this material. The decay kinetics of the PPC effect can be well described by the stretched-exponential function IPPC(t)=IPPC(0)exp[-(t/τ)β], (0<β<1), which is similar to the behavior observed in many disorder systems. Through the study of the PPC effect under various conditions, and combining with the characteristics of the PL spectra, we identify that the origin of the PPC effect arises from the spatial separation of photoexcited electrons and holes. Here, the photoexcited electrons fall into the GaAs layer, and holes are trapped by local potential minima due to alloy fluctuations in the GaAsSb layer. This process prevents the recombination of electrons and holes, and thus the PPC occurs. In order to return to the initial states, photoexcited electrons have to overcome the energy barrier caused by the conduction band offset. [ABSTRACT FROM AUTHOR]

Temperature dependent photoreflectance (PR) and photoluminescence experiments of the InAs/GaAs quantum dot (QD) structures were performed. At 20 K, effective band-gap transitions due to the InAs QDs, wetting layers, and GaAs buffer and cap layers were identified. Transition energies of the ground state and four excited states with nearly equal interlevel spacings (75–80 meV) were observed. The linewidth of the ground-state transition decreased as the temperature increased from 20 K to 100 K while the linewidth became broader at temperatures above 100 K. Energy features of the PR spectra originating from QDs and relating to the in-plane parabolic potentials were discussed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Anisotropic property of type-II GaAs/GaAsSb heterostructures was studied by photoluminescence (PL) and photoconductivity (PC). It was found that the PL and PC spectra exhibit a strong in-plane polarization with respect to 〈011〉 axis with polarization degrees up to 40%. We showed that the polarization does not depend on the excitation intensity as well as temperature, which excludes any extrinsic mechanisms related to the in-plane anisotropy. The observed polarized optical properties of GaAsSb/GaAs multiple quantum wells was attributed to the intrinsic property of the orientation of chemical bonds at heterointerfaces. [ABSTRACT FROM AUTHOR]

It is well known that nitrogen incorporation into III–V compounds will degrade the quality of materials. In this letter, we show that the incorporation of atomic hydrogen into InAsN/InGaAs quantum wells can effectively passivate defects and lead to enhancement of photoluminescence intensity near the band edge. After hydrogenation, the change of the optical properties is quite different from that of the annealing with nitrogen treatment. For instance, the linewidth becomes wider after hydrogenation, while the linewidth is narrower after nitrogen annealing. Through a detailed study of the photoluminescence spectra, we show that the passivation of defect bonds is the main reason for the improved optical behavior for hydrogenation, while the interdiffusion is responsible for the change after nitrogen annealing. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]