Anomalous Capacitance in Gallium Phosphide Electroluminescent p-n Junctions

Anomalous capacitance-voltage and current-voltage characteristics have been observed in GaP p - n junctions. Capacitance in these diodes abruptly decreases in the forward direction when the applied voltage exceeds 1.5 V, and is largely frequency-dependent above 100 kHz. Moreover, both capacitance and parallel conductance are temperature-dependent above 100 kHz. The observed anomalies have quantitatively been explained by a model in which deep centers take part in space charges in the depletion layer. The deep centers are considered to be acceptors due to Ga vacancies produced by zinc diffusion which occurs during junction formation by liquid phase epitaxy or during heat treatment, and to be distributed in the p -side. Analyses of experimental data have revealed that the junction has a p -π- i - n structure and that, in the π-layer, the deep acceptor concentration is predominantly high as compared with the net shallow acceptor concentration. Voltage dependence of diode current and red electroluminescence has also been interpreted in terms of this junction structure.