Electron beam electroreflectance studies of GaAs and CdTe surfaces

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Abstract
An electron beam electroreflectance (EBER) system has been built and used to investigate GaAs and CdTe sample surfaces. EBER permits one to go to low temperatures, to couple electroreflectance with high-vacuum techniques and to study the effects of different surface treatments. Analysis shows that the EBER technique leads to only negligible thermal modulation of the sample for low-energy electron beams such as that used here. The results of our measurements before and after sputtering with 2 keV O+2 ions clearly show that the measurements are very sensitive to the condition of sample surfaces. Analysis of the results shows the existence of distinct surface and bulk signals and gives detailed information about the surface before and after sputtering. Comparison of our EBER results with room-temperature electrolyte-electroreflectance results on both GaAs and CdTe confirms the analysis and establishes that electroreflectance is a surface-sensitive technique.