As a promising new class of near-infrared light emitters, GaAsBi laser diodes (LDs) are considered to have a high energy efficiency and an insensitive temperature dependence of the band gap. In this paper, we realize the longest ever reported lasing wavelength up to 1.142 μm at room temperature in GaAsBi 0.058 /GaAs quantum well LDs grown by molecular beam epitaxy. The output power is up to 127 mW at 300 K under pulsed mode. We also demonstrate continuous wave mode operation up to 273 K for the first time. The temperature coefficient of the GaAsBi/GaAs LD is 0.26 nm/K in the temperature range of 77−350 K, lower than that of both InGaAsP/InP and InGaAs/GaAs LDs. The characteristic temperature is extracted to be 139 K in the temperature range of 77−225 K and decreases to 79 K at 225−350 K.
Highly tensile-strained Ge quantum
dots (TS-Ge-QDs) emitting structures
with different size were successfully grown on InP substrates by molecular
beam epitaxy. Dislocation-free TS-Ge-QDs were observed by transmission
electron microscopy. Finite element modeling indicates a maximum tensile
strain of 4.5% in the Ge QDs, which is much larger than the required
strain to achieve direct band gap conversion of Ge based on theoretical
prediction. Photoluminescence (PL) from a direct band-gap-like transition
of TS-Ge-QDs with a peak energy of 0.796 eV was achieved and confirmed
by the etch depth-dependent PL, temperature-dependent PL, and excitation-power-dependent
PL. In addition, a strong defect-related peak of 1 eV was observed
at room temperature. The band structure of the TS-Ge-QDs emitting
structures was calculated to support the experimental results of PL
spectra. Achieving PL from direct band-gap-like transitions of TS-Ge-QDs
provides encouraging evidence of this promising highly tensile strained
semiconductor-nanostructure-based platform for future photonics applications
such as integrated light sources.
High quality AlAs 1−x Bi x layers with Bi composition of 3%-10.5% have been successfully grown by molecular beam epitaxy. The Bi incorporation is confirmed by Rutherford backscattering spectroscopy. For a 400 nm thick AlAsBi layer, the strain relaxation occurs when the Bi composition is larger than 6.5%. Flux ratio is calculated from Knudsen-cell model and Maxwell equation, according to the geometrical relationship of our equipment. The Bi incorporation increases with increasing the As-Al flux ratio as well as the Bi flux. The extrapolation lattice constant of hypothetic zincblende AlBi alloy is about 6.23 Å.
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