Dependence of Biasing Voltage and Illumination Power on the Built-in Electric Field of InGaP Solar Cells

The electroreflectance spectra of InGaP solar cells at various biasing voltages and illumination levels were studied. The Franz--Keldysh oscillations were observed and the electric field at the junction of solar cells can be extracted. The measured electric field decreases with increasing biasing voltage and illumination level. The theoretical electric fields as a function of the biasing voltage and the photocurrent are calculated on the basis of the depletion approximation in the junction theory and the photovoltaic effect, respectively.