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

Photoreflectance has been used to study the Fermi-level of annealed low temperature (200 degrees C) grown GaAs which is passivated on Si-delta-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-delta-doped layer. The annealing temperature of the low temperature cap is 600-900 degrees 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 degrees C to 900 degrees C. These results are connected to the arsenic precipitation at the different annealed temperatures.