Tunnel-modulated Ge LED/laser light source and a sub-thermal voltage switching detector for the monolithic on-chip optical transceiver

We report on the fabrication of a Ge on Si photonic (SiP) device enabling light emission under reverse bias and light detection at forward bias, enabled by low-voltage switching Ge tunnel diodes (TDs) — The Zener-Emitter (ZE) [1] and the Esaki-Collector (EC). The devices enable for the first time monolithic, highly efficient electrical-to-optical (E/O; Cs = 114 mV/dec) and optical-to-electrical (O/E; Cs = 31 mV/dec) signal conversion since the TDs control carrier injection and extraction. The light source (ZE) is realized as an ultra-fast LED (f > 1 GHz) and as a cavity enhanced Laser source with P
out
= 1.6 mW output power. The carrier-collection efficiency in the detector (EC) is enhanced by the Esaki tunnel junction, while the rapid turn-off is induced by the negative-differential resistance (NDR; f > 22 GHz), enabling sub-thermal voltage switching.