The infrared sensing MOSFET

Experimental results are presented on the operation of gold-, indium-, and gallium-doped silicon MOSFET´s as infrared photon detectors (IRFET´s) [1]. Photoionization of these impurity centers in the surface space charge depletion region of the MOSFET causes a modulation in the threshold voltage and the conductivity of the MOSFET. Previous results on gold-doped devices [2,3] have been extended to indium-doped devices [4] and preliminary results obtained on gallium-doped devices. The IRFET exhibits large gains and responsivities of 1.0 milliamp/microwatt (10 milliwatts/microjoule) are easily achieved with indium-doped devices. It is shown that shot noise or background limited rather than 1/f noise limited operation can be achieved. By the use of these three dopants, the near, middle, and far infrared wavelength regions can be covered.