20 μm cutoff heterojunction interfacial work function internal photoemission detectors

Results are reported on Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors designed for operation up to 20 μm. The peak response of 100 mA/W at 12.5 μm with a D* of 2×1011 Jones was observed with a cutoff wavelength of ∼20 μm. The BLIP temperature for the devices was 40 K at 1.5 V bias. While the peak response remained almost constant (∼95 mA/W) up to 40 K, the D* reduced to 5×109 Jones due to the increased dark current. The response increased with doping while the dark current did not change significantly. Hence, higher responsivity and D* can be expected for designs with higher doping. Designs utilizing increased reflection from the bottom contact are suggested to improve the resonant cavity enhancement for optimizing the detectors, which should lead to higher D* and BLIP temperature.