GaAsBi has been researched as a candidate material for optoelectronic devices for around two decades. Bi‐induced localized states induce a rapid rising of the valence band edge through a band anticrossing interaction, which has a profound effect on the bandgap and the spin–orbit splitting. The band engineering possible, even with just a few percent bismuth, makes GaAsBi an attractive material for THz emitters, telecommunication lasers, and low noise photodetectors, among other devices. There has been substantial progress in some of these areas; however, progress toward many of the potential applications of GaAsBi has been hindered by device quality issues, brought about by the low substrate temperatures necessary for the growth of GaAsBi with sufficiently large Bi fractions. This review, presents an overview of the applications for which GaAsBi has been advocated and the key results in these areas. The molecular beam epitaxy growth and postgrowth processing of GaAsBi are then explored as well as the novel techniques that have been suggested to improve material quality.

Avalanche Photodiodes (APDs) are key semiconductor components that amplify weak optical signals via the impact ionization process, but this process’ stochastic nature introduces ‘excess’ noise, limiting the useful signal to noise ratio (or sensitivity) that is practically achievable. The APD material’s electron and hole ionization coefficients (α and β respectively) are critical parameters in this regard, with very disparate values of α and β necessary to minimize this excess noise. Here, the analysis of thirteen complementary p-i-n/n-i-p diodes shows that alloying GaAs with ≤ 5.1 % Bi dramatically reduces β while leaving α virtually unchanged—enabling a 2 to 100-fold enhancement of the GaAs α/β ratio while extending the wavelength beyond 1.1 µm. Such a dramatic change in only β is unseen in any other dilute alloy and is attributed to the Bi-induced increase of the spin-orbit splitting energy (∆so). Valence band engineering in this way offers an attractive route to enable low noise semiconductor APDs to be developed.

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GaAsBi has been researched as a candidate material for optoelectronic devices for around two decades. Bi-induced localized states induce a rapid rising of the valence band edge through a band anti-crossing interaction, which has a profound effect on the band gap and the spin orbit splitting. The band engineering possible, even with just a few percent bismuth, makes GaAsBi an attractive material for THz emitters, telecommunication lasers, and low noise photodetectors, among other devices. There has been substantial progress in some of these areas; however, progress towards many of the potential applications of GaAsBi has been hindered by device quality issues, brought about by the low substrate temperatures necessary for the growth of GaAsBi with sufficiently large Bi fractions. In this review, we present an overview of the applications for which GaAsBi has been advocated and the key results in these areas. We then explore the molecular beam epitaxy growth and post-growth processing of GaAsBi and the novel techniques that have been suggested to improve material quality. IntroductionReceived: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Indium arsenide quantum dots are of great interest for next-generation telecom optoelectronics if their emission wavelength can be red shifted into the correct range. One method to achieve this is the deposition of a surfactant, such as bismuth, during quantum dot growth. Here, we present a series of indium arsenide quantum dot layers grown using several bismuth fluxes and two different growth temperatures. The effects of bismuth flux on quantum dot morphology and optical properties are studied by atomic force microscopy and photoluminescence measurements. Bimodal distributions of quantum dots are seen at low growth temperature, while at high temperature, a single dominant distribution is seen in most of the layers. A medium bismuth flux was seen to produce the highest integrated photoluminescence intensity at high growth temperature, whereas intensity saturates between medium and high fluxes at low growth temperatures. A significant increase in uncorrected aspect ratio seen for the layer grown with a low bismuth flux at high growth temperature presents a new opportunity for control of quantum dot morphology using bismuth.

A series of gallium arsenide bismide device layers covering a range of growth conditions are thoroughly probed by low-temperature, power-dependent photoluminescence measurements. The photoluminescence data is modelled using a localised state profile consisting of two Gaussians. Good agreement with the raw data is achieved for all layers whilst fixing the standard deviation values of the two Gaussians and constraining the band gap using X-ray diffraction data. The effects of growth temperature and bismuth beam equivalent pressure on the localised state distributions, and other model variables, are both shown to be linked to emission linewidth and device properties. It is concluded that bismuth rich surface conditions are preferable during growth in order to produce the narrowest emission linewidths with this material. These results also show how the growth mode of a gallium arsenide bismide layer can be inferred ex-situ from low-temperature photoluminescence measurements.