Selective epitaxial germanium on silicon-on-insulator high speed photodetectors using low-temperature ultrathin Si0.8 Ge0.2 buffer

Abstract

The authors report the performance of selective epitaxial Ge (400 nm) on Si-on-insulator p-i-n mesa-type normal incidence photodiodes using ∼14 nm low-temperature Si0.8 Ge0.2 buffer without cyclic annealing. At -1 V, very low bulk dark current densities of 1.5-2 mA cm2 were obtained indicating good material quality, and the peripheral surface leakage current densities were 14-19.5 μAcm. For 28 μm diameter round photodiode, the highest achieved external quantum efficiencies at -5 V were 27%, 9%, and 2.9% for 850 nm, 1.3 μm, and 1.56 μm optical wavelengths, respectively. 15×15 μ m2 square photodiode has 3 dB bandwidth 15 GHz at -1 V. Good performance was achieved without high-temperature annealing, suggesting easy integration of GeSi photodiode unto existing complementary metal-oxide-semiconductor process. © 2007 American Institute of Physics.