Time resolved photoluminescence and deep level transient spectroscopy have been used to monitor the effect of rapid thermal annealing on bulk GaInP and GaInP/AlGaInP quantum wells grown by solid source molecular beam epitaxy similar to those used in 650 nm range lasers. Following rapid thermal annealing at temperatures up to 875 °C, reductions in the concentration of several deep level traps are observed. Correlation of these data with photoluminescent intensity and lifetime measurements indicate that the defect labeled N3, 0.83 eV below the conduction band, is the dominant recombination center. The combination of these two transient spectroscopy measurement techniques is therefore not only able to measure the change in deep level concentration, but also to correlate this change with improved carrier lifetimes and, ultimately, reduced threshold current densities in quantum well lasers. There is also evidence to suggest that this same defect, possibly a phosphorous vacancy or a related complex, plays an important role in other GaInP based devices.

A high-power dual-wavelength AlGaInAs / GaAs laser operating in a vertical external-cavity surface emitting geometry, grown by molecular beam epitaxy, is reported. The active regions of the laser are separated by an optical long-wave-pass filter to prevent absorption of short-wavelength radiation in the long-wavelength gain area. The maximum output power achieved at 15 degrees C was 0.75 W at lambda approximately 966 nm and 1.38 W at lambda approximately 1047 nm for the pump power of 21.2 W.

Electronic and structural properties of GaAs͑100͒͑2 ϫ 4͒, InAs͑100͒͑2 ϫ 4͒, and Sb/ InAs͑100͒͑2 ϫ 4͒ reconstructed surfaces have been studied by synchrotron-radiation photoelectron spectroscopy and scanning tunneling microscopy ͑STM͒. Based on the difference spectrum of As 3d core-level spectra of III-As͑100͒͑2 ϫ 4͒, measured in different surface-sensitivity conditions, as well as the line shape of the As 3d emission from the Sb-induced ͑2 ϫ 4͒ surface, we give evidence that the As 3d spectra of GaAs͑100͒͑2 ϫ 4͒ and InAs͑100͒͑2 ϫ 4͒ consist of two surface-core-level-shifted components. One of them is shifted about 0.2 eV to the lower kinetic energy from the bulk component. On the basis of the relative component intensities, this surface-shifted As 3d component is assigned to the emission from the first-layer As dimers in the established model of the ͑2 ϫ 4͒ surface. The other component, shifted about 0.3 eV to the higher kinetic energy, is connected to the third-layer As-dimer site. The comparison of the core-level results between GaAs͑100͒͑2 ϫ 4͒ and InAs͑100͒ ϫ͑2 ϫ 4͒ suggests that the ␣2 phase, which has one As dimer in both the first and third atomic layers per unit cell, exists on GaAs͑100͒͑2 ϫ 4͒, similarly to the case of InAs͑100͒͑2 ϫ 4͒, as predicted in theory but not observed to date. Furthermore, the STM observation of the GaAs͑100͒͑2 ϫ 4͒␣2 phase is reported.FIG. 1. Some atomic models with the cross sections for the III -V͑100͒͑2 ϫ 4͒ reconstruction: ͑a͒ ␤, ͑b͒ ␣, ͑c͒ ␤2, and ͑d͒ ␣2.PHYSICAL REVIEW B 72, 045321 ͑2005͒

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Bismuth (Bi) is a surfactant which controls the electronic and structural properties of epitaxially grown GaInAs and GaInP alloys. The authors have studied Bi-terminated surfaces of GaInAs(100) layers, deposited onto InP(100) substrates, by means of scanning tunneling microscopy and spectroscopy and x-ray photoelectron spectroscopy. It appears that Bi stabilizes an interesting (2×1) surface reconstruction on GaInAs(100). Under certain conditions, this reconstruction undergoes a phase transition to (2×4), which has about one-half of the Bi content of the (2×1) surface. Based on the experimental findings, they discuss mechanisms leading to this phase transition.