MBE growth and doping of AlGaP

In this work, we investigate the impact of growth parameters on surface morphology, doping levels and dopant activation in AlGaP epilayers grown on GaP substrate by solid source molecular beam epitaxy. Atomic Force Microscopy analysis reveals that a smooth surface can be obtained only in the [580-680] °C growth temperature range for a sufficiently large V/III ratio. From C(V), Hall measurements and SIMS analysis, it is shown that a reasonable activated p-doping (Be) value (typically 1018 cm−3) can be reached if the growth temperature remains larger than 580 °C. For the n-doping (Si), the situation is much more critical, as a growth temperature below 650 °C leads to a strongly insulating layer. This dopant activation issue is related to the appearance of deep traps that are generated when growth temperature is not high enough, as evidenced by deep level transient spectroscopy and isothermal deep level transient spectroscopy. It is therefore suggested that electrically-driven devices using AlGaP epilayers have to be carefully designed in order to match both roughness and dopants activation constraints on growth temperatures and growth rates.