GeSn/Ge multiquantum-well vertical-cavity surface-emitting p-i-n structures and diode emitters on a 200 mm Ge-on-insulator platform

Abstract

An efficient monolithically integrated light source with complementary metal-oxide semiconductor (CMOS) compatibility remains the missing component to enable Si photonics for various applications. In particular, vertical-cavity-surface-emitting (VCSE) light sources, such as resonant cavity light-emitting diodes (RCLEDs) and vertical cavity surface-emitting lasers (VCSELs), are strong contenders due to their compact size, circular emission profile with low beam divergence, wafer-scale fabrication compatibility, high bandwidth and high coupling efficiency to fiber optic cables. We report the first demonstration of 8-inch wafer-scale GeSn/Ge multiple-quantum-well VCSE p-i-n structures and diodes for laser or light-emitting diode (LED) applications in Si photonics by wafer bonding and layer transfer techniques, which are challenging for all-epitaxy routes. Alternative dielectric layers (SiO2/SiN/SiO2), introduced by wafer bonding, under the emitting structure serve as the bottom mirror for the vertical cavity. The Ge0.92Sn0.08/Ge MQW layer is utilized to improve the material quality and to confine injected carries. As a result, more than 8× enhancement of light emission due to the vertical cavity resonance was demonstrated by photoluminescence spectroscopy. Besides, the spectral purity is enhanced by the single-mode cavity. The intensity of light emission is insensitive to the temperature range from 4 to 300 K and even becomes stronger at higher temperatures. The vertical cavity effect on the light emission is further verified by reflectivity spectroscopy and optical simulations. A positive gain can be achieved as indicated by optical gain calculations and an excellent carrier injection efficiency of the MQW VCSE diode is observed, showing its potential for electrically injected RCLEDs and VCSELs.