Photon Drag Effect in Germanium

Abstract

It is described how the photon drag voltage in germanium varies with hole concentration and how it depends on temperature. Also some considerations are taken into the following additional contributions similar to the photon drag effect: (1) the Thomson effect, (2) the hot carrier effect and (3) the diffusion effect. Experiments were performed by using a Q-switched CO 2 laser. This photon drag effect provides a convenient detector for use with Q-switched CO 2 lasers and mode-locked CO 2 lasers, because it operates with the high speed response time smaller than 10 -10 s at room temperature. In the case of p -type germanium with the resistivity of 2.3 Ω-cm and the size of 1.5×1.5×20 mm 3 , its responsivity ( R ) is 3×10 -6 (V/W) and the detectivity ( D ) is 1.4×10 3 (W -1 ) at room temperature and 1.1×10 4 (W -1 ) at 77 K.