Time-resolved photoluminescence was performed on as-grown and annealed bulk GaAsBi samples. Rapid thermal annealing was carried out at a temperature of 750 • C. With annealing, we observed a significant change in the photoluminescence decay time at low temperature and low excitation power, which is likely due to a reduction of localized states. Although the time-integrated photoluminescence intensity did not show a large variation, this enhancement was confirmed by the observed removal after annealing of the S-shape behaviour present in the as-grown sample.
We have grown GaAsBi quantum wells by molecular beam epitaxy. We have studied the properties of a 7% Bi GaAsBi quantum well and their variation with thermal annealing. High-resolution X-ray diffraction, secondary ion mass spectrometry, and transmission electron microscopy have been employed to get some insight into its structural properties. Stationary and time-resolved photoluminescence shows that the quantum well emission, peaking at 1.23 μm at room temperature, can be improved by a rapid annealing at 650°C, while the use of a higher annealing temperature leads to emission degradation and blue-shifting due to the activation of non-radiative centers and bismuth diffusion from the quantum well.
Electron spin dynamics in elastically strained bulk GaAsBi epilayer with 2.2% Bi concentration has been measured by time resolved photoluminescence spectroscopy. Under external transverse magnetic field, the measurement of the photoluminescence polarization oscillations resulting from the Larmor precession of electron spins yields an accurate determination of the Landé g-factor. We find that the value of g increases from −0.81 to −0.68 when the temperature rises from T = 100 K to T = 300 K. This is typically double the value of GaAs, in agreement with the larger spin-orbit interaction in GaAsBi. In this temperature range, the electron spin lifetime decreases from 370 to 100 ps.
The fabrication of self-assembled InGaAs squarelike nanoholes on GaAs(001) substrates grown by droplet epitaxy using molecular beam epitaxy was reported. The formation mechanism is explained by the As4 diffusion in droplets during the supply of As4 flux. The effects of substrate temperature (300–390 °C) during the InGa droplet deposition on their dimension and density were investigated. The surface morphology of InGaAs nanoholes as well as their depth profile was examined by atomic force microscopy (AFM). The square shape is oriented along [110] and [110] crystallographic directions with slightly different profiles due to anisotropy behavior. The size uniformity of the squarelike nanoholes is well controlled with less deviation at higher substrate temperatures.
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