Performance Comparison of Top- and Bottom-emitting Long Wave Infrared Light Emitting Diode Devices

Electroluminescence in the range of 5-10 mu m with peak emission at 8 mu m from an Sb-based type II interband quantum cascade structure is reported. We used both top- and flip-chip-mount bottom-emitting long wave infrared (LWIR) light emitting diode (LED) devices. An increase in light emission was observed by thinning the GaSb substrate material for both top- and bottom-emitting devices. For a similar GaSb substrate thickness, a flip-chip-mount bottom-emitting LED device had higher light emission intensity than a top-emitting device. Higher emission intensity for the bottom-emitting device was attributed to better cooling and to reflection of light from the anode metal surface in the LED mesa area.