Sub-terahertz response of stressed and unstressed Ge:Ga photoconductive detectors

Abstract

Ge:Ga is a widely used detector material for applications at terahertz frequencies. Its response ranges from about 40 µm - 120 µm. If a compressive force is applied to the crystal the response shifts to about 100 µm - 240 µm. We report on a long wavelength, sub-terahertz response > 300 µm. This response can be attributed to transitions from excited Ga states into the valence band. The results indicated that a cascade type of relaxation exists in Ge:Ga at 4.5 K