Growth of GalnTlAs layers on InP by molecular beam epitaxy

Growth of GaInTlAs alloys on InP(001) has been attempted by solid source mo lecular beam epitaxy. Thallium incorporation into Ga1-xInxAs matrices was s tudied as a function of substrate temperature, arsenic overpressure, matrix composition, and growth rate. At high temperatures (> 350 degreesC) thalli um evaporates, whereas at intermediary temperatures (270-350 degreesC) thal lium segregates into droplets on the surface. Only in the low temperature r ange (180-260 degreesC) can thallium be incorporated ill some conditions, l eading to mirror-like surfaces. Up to 18% Tl content was incorporated into a Ca0.70In0.30As matrix and up to 40% Tl into a GaAs matrix. For these high Tl concentrations, Tl droplets are avoided and Tl incorporation is achieve d only when using high arsenic pressures. However, this limits surface adat om diffusion and leads to amorphous, polycrystalline, or twinned materials. Finally, a narrow window for single-crystal growth has been found for low Tl contents (4%) using optimized growth conditions with low V/III pressure ratios and high growth rates. (C) 2001 American Vacuum Society.