Photoreflectance of low-temperature-grown GaAs on Si-δ-doped GaAs

Photoreflectance has been used to study the Fermi-level of annealed_ lovv temperature (200°C) grown GaAs which is passivated on Si-δ-doped GaAs. The Fermi-level of the samples are measured by the photovoltaic effect of the built-in electric field between the interface of the low temperature grown cap layer and the Si-δ-doped layer. The annealing temperature of the low temperature cap is 600-900°C. The Fermi-levels of annealed low temperature GaAs are found to decrease from 0.55 eV to 0.40 eV below the conduction band when the annealing temperatures are increased from 600°C to 900°C. These results are connected to the arsenic precipitation at the different annealed temperatures.