Impact Ionization Coefficients in

Electron and hole multiplication characteristics have been measured on a series of Al_0.52In_0.48P p⁺-i-n⁺ and n⁺-i-p⁺ homojunction diodes with nominal avalanche region thicknesses ranging from 0.22 to 1.03 μm. From these, the electron and hole impact ionization coefficients are deduced over an electric-field range from 530 to 990 kV/cm. The results suggest that the electron ionization coefficient is larger than the hole ionization coefficient, particularly at lower electric fields. Extremely low dark currents were obtained, and there was no evidence of any tunneling dark current even at electric fields of approximately 1.0 MV/cm. From these ionization coefficients, we deduce that the breakdown voltage in Al_0.52In_0.48P is almost 2.5× greater than that of GaAs and 4.5× lower than that of GaN.