We report a GaAsBi/GaAs multiple quantum well (MQW) light emitting diode (LED) grown by molecular beam epitaxy using a two-substrate-temperature (TST) technique. In particular, the QWs and the barriers in the intrinsic region were grown at the different temperatures of [Formula: see text] = 350 °C and [Formula: see text] respectively. Investigations of the microstructure using transmission electron microscopy (TEM) reveal homogeneous MQWs free of extended defects. Furthermore, the local determination of the Bi distribution profile across the MQWs region using TEM techniques confirm the uniform Bi distribution, while revealing a slightly chemically graded GaAs-on-GaAsBi interface due to Bi surface segregation. Despite this small broadening, we found that Bi segregation is significantly reduced (up to 18% reduction) compared to previous reports on Bi segregation in GaAsBi/GaAs MQWs. Hence, the TST procedure proves as a very efficient method to reduce Bi segregation and thus increase the quality of the layers and interfaces. These improvements positively reflect in the optical properties. Room temperature photoluminescence and electroluminescence (EL) at 1.23 μm emission wavelength are successfully demonstrated using TST MQWs containing less Bi content than in previous reports. Finally, LED fabricated using the present TST technique show current-voltage (I-V) curves with a forward voltage of 3.3 V at an injection current of 130 mA under 1.0 kA cm current excitation. These results not only demonstrate that TST technique provides optical device quality GaAsBi/GaAs MQWs but highlight the relevance of TST-based growth techniques on the fabrication of future heterostructure devices based on dilute bismides.

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Multi-quantum wells (MQWs) consisting of 3 or 3.5 pairs of nominally 8.8-nm-thick GaAs layers and 5.6-nmthick GaAs0.97Bi0.03 were grown by molecular beam epitaxy with varying the growth temperature of GaAs layers, TGaAs, and keeping the growth temperature of the GaAsBi layers at 350• C and their Bi compositional structure and optical properties were investigated. Analysis of x-ray diffraction spectra reveals that 67% of the total Bi atoms supplied during growth of a single GaAsBi layer were segregated on the growing surface and were incorporated into the successive GaAs layer at TGaAs = 350• C. The GaAs layers at TGaAs = 450 and 500• C contained 17% of the Bi atoms totally supplied and 50% of them were evaporated. Almost all Bi atoms segregated during growth of GaAsBi evaporated and were not incorporated into the GaAs layer at TGaAs = 550• C or higher. Photoluminescence (PL) spectra at 13 K shows all MQW samples have good optical quality and the MQW sample grown at TGaAs = 550• C shows the longest wavelength emission peak at 1116 nm which is 44 nm longer than the PL wavelength for the MQW grown at TGaAs = 350• C, even though the tremendous reduction of Bi incorporation into the GaAs layer grown at TGaAs = 550• C. The result strongly suggests that GaAsBi/GaAs has the type II band configuration.

Robot-assisted ureteral reconstruction using a tubularized peritoneum flap is technically feasible and reproducible. The flap sustained abundant vascular supply after different intervals of follow-up and the peritoneal mesenchymal cells differentiated into urothelium and myofibroblasts. Further studies are needed to address the issue of functional obstruction to improve long-term renal function outcomes.

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