Abstract
The effect of Furnace Annealing (FA) and Rapid Thermal annealing (RTA) on the structural and optical properties of GaAs1 − xBix/GaAs single quantum wells grown on (001) and (311)B substrates by molecular beam epitaxy was investigated. The structural properties were investigated by high-resolution x-ray diffraction (HR-XRD) and Transmission Electron Microscopy. The Bi concentration profiles were determined by simulating the HR-XRD 2θ−ω scans using dynamical scattering theory to estimate the Bi content, lattice coherence, and quality of the interfaces. The Bi composition was found to be similar for both samples grown on (001) and (311)B GaAs substrates. However, the simulations indicate that the Bi composition is not only limited in the GaAsBi quantum well (QW) layer but also extends out of the GaAsBi QW toward the GaAs barrier. Photoluminescence (PL) measurements were performed as a function of temperature and laser power for samples with a nominal Bi composition of 3%. PL spectra showed that (001) and (311)B samples have different peak energies at 1.23 eV and 1.26 eV, respectively, at 10 K. After RTA at 300 °C for 2 min, the PL intensity of (311)B and (001) samples was enhanced by factors of ∼2.5 and 1.75, respectively. However, for the (001) and (311)B FA samples, an enhancement of the PL intensity by a factor of only 1.5 times could be achieved. The enhancement of PL intensity in annealed samples was interpreted in terms of PL activation energies, with a reduction in the alloy disorder and an increase in the Bi cluster.
Highlights
Dilute bismide alloys grown on GaAs have attracted much attention due to their physical properties and potential applications in photonic devices and long–wavelength optoelectronics [1,2]
We study the effect of thermal annealing temperatures, annealing times and thermal annealing techniques on the optical and the structural properties of a GaAs(1-x)Bix/GaAs single quantum wells (QWs) grown at 320 °C by molecular beam epitaxy (MBE) on semi-insulating (001) and (311)B GaAs substrates with a nominal Bi content x = 3%
This was followed by a 10 nm thick GaAsBi single quantum wells (SQW) layer and a 50 nm GaAs cap grown at the same temperature
Summary
Dilute bismide alloys grown on GaAs have attracted much attention due to their physical properties and potential applications in photonic devices and long–wavelength optoelectronics [1,2]. In order to substitute As atoms with Bi atoms in GaAs, GaAsBi alloys are grown at low temperatures (TG = 200 °C - 400 °C) because Bi atoms are much bigger than As atoms Adopting this unconventional growth regime to incorporate Bi into the host GaAs lattice creates structural defects which behave as nonradiative centers such as native point defects and clusters [25] affecting their optical efficiency. It is well-known that post-growth thermal treatment improves the optical properties of semiconductor structures by dissociating complex defects and annihilating some other non-radiative recombination centers in order to reduce their concentrations. The incorporated Bi atoms often segregate and form Bi-rich clusters with various structures sizes in the range of 5–20 nm during thermal annealing process, depending on the Bi content and on the annealing conditions [50]
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