Germanium phototransistor with floating body

Abstract

A floating body germanium (Ge) phototransistor and associated fabrication process are presented. The method includes: providing a silicon (Si) substrate; selectively forming an insulator layer overlying the Si substrate; forming an epitaxial Ge layer overlying the insulator layer using a liquid phase epitaxy (LPE) process; forming a channel region in the Ge layer; forming a gate dielectric, gate electrode, and gate spacers overlying the channel region; and, forming source/drain regions in the Ge layer. The LPE process involves encapsulating the Ge with materials having a melting temperature greater than a first temperature, and melting the Ge using a temperature lower than the first temperature. The LPE process includes: forming a dielectric layer overlying deposited Ge; melting the Ge; and, in response to cooling the Ge, laterally propagating an epitaxial growth front into the Ge from an underlying Si substrate surface.