Ge/si (100) Heterojunction Photodiodes Fabricated From Material Grown By Low-energy Plasma-enhanced Chemical Vapour Deposition

摘要

We have fabricated a series of p-i-n Ge/Si heterojunction photodetectors with different thicknesses of the intrinsic Ge layer, different doping levels of the p and n layers and different diode diameters. Epitaxial Ge was deposited on Si(100) using low-energy plasma-enhanced CVD (LEPECVD) followed by cyclic annealing. Dark current values as low as 0.04 mA/cm~2 were achieved for 1 μm thick p-i-n photodiodes on lightly doped substrates at -1 V bias, and external quantum efficiencies of 56% at 1.30 μm and 44% at 1.55 μm for 3 (am thick p~+-i-n~+ photodiodes on highly doped substrates under 0.5 V reverse bias. For a 30 μm diameter diode a RC frequency of 21 GHz is obtained at a reverse bias of 1 V. With such characteristics, these diodes are attractive for telecommunication and optoelectronic applications.