Background limited infrared hot-electron transistor at 77 K

The authors report a background-limited photodetector (BLIP) infrared hot-electron transistor (IHET) with current density compatible with the read-out circuit at 77 K. To reduce J/sub D/ (dark current density), a novel GaAs/Al/sub x/Ga/sub 1-x/As quantum-well infrared photodetector (QWIP), in which the aluminum molar ratio of the barriers increases in three steps, has been designed. This barrier is able to suppress the dark current due to thermally assisted tunneling by providing a thicker effective when the structure is under bias. The remaining J/sub D/ is also largely eliminated by designing a bandpass filter placed adjacent to the QWIP.