High Detectivity Quantum Well Infrared Photodetectors

"High Detectivity Quantum Well Infrared§Photodetectors" was Dr. Jie Yao''s Ph.D. thesis at the§Electrical Engineering Department of Princeton§University in October 2000.§This dissertation describes the characterization,§optimization and physics of the high-detectivity§Quantum Well Infrared Photodetector (QWIP) and§Infrared Hot-Electron Transistor (IHET). §We performed high-sensitivity measurements on the§dark current and the noise current of IHETs and their§constituent QWIPs at 4.2K. The dominant noise of the§QWIPs in this regime is not from the expected shot§noise but from the 1/f noise and a bias-independent§noise. By filtering out the tunneling dark currents,§the IHETs reduce the dark current and the 1/f noise§associated with the impurity-assisted tunneling§current, and improve the detector sensitivity and§uniformity.§We optimized an infrared hot-electron transistor§(IHET) to achieve a high detectivity. This large D §is accomplished by using a low filter barrier at the§collector to achieve large photocurrent transfer§ratio. The filter barrier of the IHET blocks the§tunneling current and hence its noise at the§collector and thus improves the detector sensitivity.