Narrow Linewidth, Highly Efficient, and Integrated Light Emitting Diodes Based on Ge Quantum Dots in Optical Microcavities

摘要

Room-temperature current-injected light emitting diodes with well-resolved and narrow emission peaks are demonstrated based on Ge self-assembled quantum dots embedded in optical microcavities, including photonic crystal cavities and microdisks. By using modified L3-type photonic crystal cavities, sharp resonant peaks with Q-factor over 800 are observed in the electroluminescence spectra around wavelength of 1.3 μm. Measurable output power on the level of pico-Watt is obtained under 3 mA injected current. In order to realize integration with other on-chip photonic devices, waveguide-coupled microdisk light emitting diodes are also demonstrated. Light emission is successfully coupled from the microdisk to waveguide. Sharp resonant peaks with Q-factor over 5000 are realized. As a further step to enhance the light emission efficiency of Ge quantum dots, n-type delta-doping at Ge/Si interfaces is performed and up to 3 times enhancement of emission intensity is obtained due to extra supply of extrinsic electrons.