A high speed, low voltage silicon photodiode with buried isolation region

A new epitaxial silicon p π n photodiode that operates at biases as low as 4 V has been developed. The device has a heavily doped p⁺⁺isolation region between the p⁺substrate and the π epitaxial layer. Fast response and low leakage current result from the recombination and trapping of the minority carrier electrons in the substrate. Experimental results on such a n+π p⁺⁺p⁺device with 1.1 mm²photosensitive area show rise and fall characteristics of 3 to 4 ns at 4 V bias with 825 nm radiation. The dark current is typically 40 pA at room temperature.