High-efficiency GaAsSb/GaAlAsSb double-heterostructure hemispherical infrared emitting diodes

The material and device technology was developed for the fabrication of high-efficiency hemispherically shaped emitters consisting of a GaAsSb/GaAlAsSb double heterostructure grown on a GaAs substrate. The highest performance emitter had a radiant power out-put of 54 mW and an external quantum efficiency of 27 percent at 150-mA dc forward diode current for room-temperature operation. The peak emission wavelengths were typically 930 to 940 nm and the spectral bandwidths were 40 nm. The high efficiencies were achieved by simultaneously minimizing the two principal limitations of conventional emitters: absorption of the generated radiation before emission from the device, and total internal reflection at the semiconductor-air interface due to the mismatch of refractive indices.