The Role of Ge Wetting Layer and Ge Islands in Si MSM Photodetectors

Abstract

In this work, Ge thin films were deposited on silicon substrates by radio frequency magnetron sputtering to form Ge islands from Ge layer on Si substrate during post‐growth rapid thermal annealing (RTA). The size of the islands decreases from 0.6 to 0.1 as the rapid thermal annealing time increases from 30 s to 60 s at 900 °C. Not only that the annealing produces Ge islands but also wetting layer. Energy Dispersive X‐ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM) were employed for structural analysis of Ge islands. Metal‐Semiconductor‐Metal photodetectors (MSM PDs) were fabricated on Ge islands (and wetting layer)/Si. The Ge islands and wetting layer between the contacts of the fabricated devices are etched in order to see their effects on the device. The performance of the Ge islands MSM‐PD was evaluated by dark and photo current‐voltage (I–V) measurements at room temperature (RT). It was found that the device with island and wetting layer significantly enhance the current gain (ratio of photo current to dark current) of the device.