Quantum well infrared photodetectors (QWIP) have been developed rapidly and large QWIP arrays with 256x256 and 640x480 elements have been demonstrated. But they all use quantum well structures that consist of3O to 50 periods which have a relatively small conversion efficiency due to the small optical gain. In this paper, a high performance quantum well infrared photodetector consisting of only three quantum wells is presented which shows very large conversion efficiencies up to 29% at a bias voltage -0.8V and peak wavelength 8.5gm. A high strain twostack, two-color QWIP consists of three wells in each stack is also presented here for MWIR and LWIR detection. The MWIR stack has employed 35% of indium in the InGaAs well which not only achieved peak wavelength at 4.3j.tm, but also obtained very high peak responsivity of 0.37A/W.
Keywords: QWIP, intersubband transition, conversion efficiency, high strain