Non-uniform long-wavelength quantum well infrared photodetectors with low dark current and high BLIP temperature

Quantum well infrared photodetectors (QWIPs) based on III-V compound semiconductors have been extensively studied in recent years. The flexibility of the quantum well design and the maturity of the III-V material technology make QWIPs very attractive for long wavelength detection. However, because of the photoconductive type detection, the dark current of QWIPs is usually high and the therefore the background limited operation temperature (BLIP) is normally below 77 K. This put a severe constraint on the cooling system for QWIPs. Recently, it is reported that the electric field distribution inside a QWIP is not uniform and this phenomenon causes nonlinearity characteristics. Using this property, we have designed and fabricated a QWlP with a non-uniform quantum well structure to alter the electric field. The resulting dark current is much lower and the detectivity is much higher than those of conventional QWIPs.