Metal semiconductor metal photodiodes based on all-epitaxial Ge-on-insulator-on-Si(111), grown by molecular beam epitaxy

Abstract

We report on the fabrication and characterisation of an all-epitaxial Germanium-on-Insulator (GOI) Metal- Semiconductor-Metal (MSM) photodetector. The MSM photodetector is fabricated on a (111)-oriented epitaxial Ge layer, grown on an epitaxial Gd2O3/Si(111) substrate, by molecular beam epitaxy (MBE). The first step is the growth of the 15-nm thick Gd2O3 epitaxial layer over CMOS-grade silicon, atop which an epitaxial layer of Ge is grown. Near infrared (NIR) MSM photodetectors have been fabricated over the Ge epitaxial layer with an inter-digitated (IDT) contact structure, with an active area of 100 μm x 124 μm. For the particular IDT dimensions, the dark current has been measured to be 475 μA. A responsivity of ~ 2 mA/W is observed at a -5V bias, when excited at 1550 nm.