Patent ID: 6897471

Claim:
A biopolar band-to-band infrared photodetector-diode, or laser diode, or light-emitting diode, or amplifier, or electrooptic modulator-diode comprising (a) a silicon substrate, wherein the substrate is doped N-type or P-type while the bapping layer is doped P-type or N-type to form an NIP or PIN diode, (b) a strain-relaxed Ge 1-y Sn y or Ge 1-y-z Sn y Si z buffered layer upon Si, known as a virtual substrate, VS wherein the VS is Ge 1-y Sn y and the active region is a strain balanced type-I stack of compressive Ge 1-2y Sn2 y quantum wells with tensile Ge barriers, (c) an active direct-bandgap region made up of a single-quantum-well heterostructure or a multi-quantum-well stack, (d) a strain-relieved capping layer of Ge 1-y Sn y or Ge 1-y-z Sn y Si z , matching the VS composition, (e) metallic electrical contacts to the Si substrate and capping layer.