GeSn resonant-cavity LEDs

Researchers in Taiwan report room-temperature mid-infrared resonant electroluminescence from germanium tin (GeSn) resonant-cavity light-emitting diodes (RCLEDs) with a lateral p-i-n configuration on a silicon-on-insulator.

Group IV light emission is hampered by the indirectness of the bandgap, which inhibits electron-hole recombination into photons. However, the Ge energy band structure has a direct valley at the Γ point that is only 136.5meV higher than the indirect L-valley.

The team theoretically calculated that the band structure of GeSn with 4.3% Sn content and 0.52% compressive strain showed a decrease in the energy difference between the conduction-band valleys at the direct Γ point and in the L-direction to 89meV