Non-stoichiometric GaAsBi/GaAs (100) molecular beam epitaxy growth

The growth of III–V bismuthides is complicated by the low incorporation efficiency of Bi in GaAs, leading either to the formation of metallic Bi droplets or low layer composition fractions. Typically growth is performed between 280 and 350 °C and at near stoichiometric Ga:As fluxes in order to encourage Bi incorporation. However most work reported to date also utilises As2 as the As overpressure constituent. It is found in this work that growth with As4 allows high Bi composition films with the standard 1:20 Ga:As4 beam equivalent pressure ratio (BEPR) utilised for higher temperature buffer layer growth. The Bi fraction versus Bi:As4 BEPR is found to be initially linear, until a maximum value is obtained for a given temperature after which the continued oversupply of Bi results in the formation of droplets.

► Droplet free growth of GaAsBi.
► High temperature growth of GaAsBi.
► Growth with As4 overpressure, not As2.
► Optimisation of growth recipe for (a) strong photoluminescence intensity, (b) narrow FWHM and (c) crystal quality (XRD data).