Photoconductors for 200–400 μm: Choices and challenges

Extrinsic silicon and germanium photoconductors are the most sensitive detectors of far infrared radiation. This paper surveys various options being considered to extend the wavelength coverage of extrinsic photoconductors beyond the current limit of 220 μm. The benefits, current status, and potential limitations of Ge: Ga blocked impurity band detectors, GaAs extrinsic photoconductors and GaAs blocked impurity band detectors are reviewed.