Ion-implanted Ge:B far-infrared blocked-impurity-band detectors

Ge blocked-impurity-band (BIB) photoconductors have the potential to replace stressed Ge:Ga photoconductors for far-infrared astronomical observations. A novel planar BIB device has been fabricated in which ion-implanted boron is used to form the blocking contact and absorbing layers of necessary purity and compensation. The effect of doping in the infrared active layer on the far-infrared photoconductive response has been studied, and the optimum doping concentration is found to be ∼4 × 1016 cm−3. Devices doped near this concentration show good blocking characteristics with low dark currents. The spectral response extends to ∼45 cm−1, clearly showing the formation of an impurity band. Under low background testing conditions these devices attain a responsivity of 0.12 A/W and NEP of 5.23 × 10−15 W/Hz1/2.