Optical monitoring of the growth of heavily doped GaAs by chemical beam epitaxy and of the in   situ etching of GaAs using CBr4

We report the in situ optical monitoring of the growth of heavily doped GaAs by chemical beam epitaxy. The normal incidence reflectance of a 670 nm semiconductor laser was monitored in real time using dynamic optical reflectivity (DOR). Oscillations in the reflectance of the growing film arising from small changes in the refractive index due to doping were observed for carbon doping in the range 2×1019–6×1020 cm−3. No oscillations were obtained for samples with carbon or sulphur doping levels in the range 1018–1019 cm−3. A reduction in growth rate was observed for carbon concentrations above 1020 cm−3 and this was attributed to etching by the CBr4 dopant source. In situ etching of GaAs layers by CBr4 prior to growth was also monitored using DOR.