Ge:Ga Far-Infrared Photoconductor with Low Compensation

A sensitive Ge:Ga photoconductor was developed, and the performance of the far-infrared detector was studied for application to astronomical and atmospheric observations using stratospheric balloons. The Ge:Ga photoconductor had a response up to 110-µm wavelength and a high responsivity of R = 8.0 A/W at 4.2 K. The product of quantum efficiency and photoconductive gain ηG was 0.11, and the photoconductive gain G was estimated to be 0.36 at a half bias field of breakdown. The N E P was 8.5 × 10-16 W/√Hz operated at 4.2 K. Both the resistivity and the breakdown field of the Ge:Ga detectors showed that the compensation of this crystal K=N d/N a (donor concentration/acceptor concentration) was rather low, that is, less than 10-2. The Photoconductor's high responsivity could be attributed to the high photoconductive gain produced by the low compensation.