A three-well quantum well infrared photodetector

A simplified quantum well infrared photodetector (S-QWIP) has been designed and demonstrated which shows very high performance. The S-QWIP is designed to have only three quantum wells with detection peak wavelengths at 7.3, 8.3, and 10 mu m, for the first, second, and third well, respectively. The two barriers between the three wells are graded to block the dark current effectively when reverse bias is applied. It also produces a built-in potential in the structure for a photovoltaic (PV) effect. The two end barriers are designed with different widths so that the electron transport call be compared when the bias directions are changed. The responsivity of the S-QWIP shows three photoreponse peaks at zero bias (PV effect) and migrates to one wide peak when the bias increases. The device is BLIP at 85 K within the operable reverse bias range. The responsivity is greatly enhanced at higher temperature and small bias. The conversion efficiency of photon absorption to photocurrent calculated conservatively at a bias voltage -0.8 V and peak wavelength 8.5 mu m is 29%. (C) 1996 American Institute of Physics.