In this work we used a combination of photoluminescence (PL), high resolution X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) techniques to investigate material quality and structural properties of MBE-grown InGaAsBi samples (with and without an InGaAs cap layer) with targeted bismuth composition in the 3-4% range. XRD data showed that the InGaAsBi layers are more homogenous in the uncapped samples. For the capped samples, the growth of the InGaAs capped layer at higher temperature affects the quality of the InGaAsBi layer and bismuth distribution in the growth direction. Low temperature PL exhibited multiple emission peaks; the peak energies, widths and relative intensities were used for comparative analysis of the data in line with the XRD and RBS results. RBS data at random orientation together with channelled measurements allowed both an estimation of the bismuth composition as well as analysis of the structural properties. The RBS channelling showed evidence of higher strain due to possible anti-site defects in the capped samples grown at a higher temperature. It is also suggested that the growth of the capped layer at high temperature causes deterioration of the bismuth-layer quality. The RBS analysis demonstrated evidence of a reduction of homogeneity of uncapped InGaAsBi layers with increasing bismuth concentration. The uncapped higher bismuth concentration sample showed less defined channelling dips suggesting poorer crystal quality and clustering of bismuth on the sample surface.

A key component for the realization of silicon-photonics are integrated lasers operating in the important communications band near 1.55 µm. One approach is through the use of GaSb-based alloys which may be grown directly on silicon. In this study, silicon-compatible strained Ga0.8In0.2Sb/Al0.35Ga0.65As0.03Sb0.97 composite quantum well (CQW) lasers grown on GaSb substrates emitting at 1.55 μm have been developed and investigated in terms of their thermal performance. Variable temperature and high-pressure techniques were used to investigate the influence of device design on performance. These measurements show that the temperature dependence of the devices is dominated by carrier leakage to the X minima of the Al0.35Ga0.65As0.03Sb0.97 barrier layers accounting for up to 43% of the threshold current at room temperature. Improvement in device performance may be possible through refinements in the CQW design, while carrier confinement may be improved by optimization of the barrier layer composition. This investigation provides valuable design insights for the monolithic integration of GaSb-based lasers on silicon.

Type-II ‘W’-lasers have made an important contribution to the development of mid-infrared laser diodes. In this paper, we show that a similar approach can yield high performance lasers in the optical communications wavelength range. (GaIn)As/Ga(AsSb) type-II ‘W’ structures emitting at 1255 nm have been realised on a GaAs substrate and exhibit low room temperature threshold current densities of 200–300 A cm−2, pulsed output powers exceeding 1 W for 100 µm wide stripes, and a characteristic temperature T 0 ≈ 90 K around room temperature. Optical gain studies indicate a high modal gain around 15–23 cm−1 at 200–300 A cm−2 and low optical losses of 8 ± 3 cm−1. Analysis of the spontaneous emission indicates that at room temperature, up to 24% of the threshold current is due to radiative recombination, with the remaining current due to other thermally activated non-radiative processes. The observed decrease in differential quantum efficiency with increasing temperature suggests that this is primarily due to a carrier leakage process. The impact of these processes is discussed in terms of the potential for further device optimisation. Our results present strong figures of merit for near-infrared type-II laser diodes and indicate significant potential for their applications in optical communications.

The incorporation of dilute amounts of Bi into the host lattice of a III/V semiconductor has a strong influence on its electronic properties. The bandgap is strongly redshifted which makes these materials interesting for application in the near- to mid-infrared regime. Furthermore, the spin-orbit splitting is increased resulting in suppression of hot-hole producing Auger recombination, which makes the fabrication of highly efficient optical devices feasible. However, for ternary Ga(As,Bi) grown using metalorganic vapor phase epitaxy (MOVPE), it has proven difficult to achieve the desired composition of the ternary material. Therefore, the additional incorporation of indium (In) into Ga(As,Bi), which should induce a further redshift of the bandgap, is investigated and summarized in this paper. For deposition of quaternary (Ga,In)(As,Bi), two different low temperature growth techniques using MOVPE are conducted. The strain and photoluminescence peak positions of the samples are correlated to estimate the composition of the (Ga,In)(As,Bi) layers. It was found that the trimethylindium and tertiarybutylarsine supplies need to be carefully adjusted to grow high quality bulk materials and that the incorporation of indium is inversely related to the amount of incorporated Bi.

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