High Purity Germanium Radiation Detectors

Abstract
The fabrication and characterization of high purity germanium radiation detectors are described. These detectors are n-i-p diodes with a shallow (1.5μ) diffused junction and a noninjecting metal-semiconductor contact. The germanium has a net acceptor concentration of approximately 7 × 1011 cm-3 and contamination during processing was prevented by using clean procedures and a KCN treatment. Electrical measurements show that with 500 volts of bias these detectors are fully depleted and have a capacitance of approximately 4.5 pf. Detection characteristics are determined from measurements of γ-rays and x-rays over the energy range of 6 keV to 136 keV. A deviation from linearity of less than ± 0.2 percent was measured. The resolution of the detectors is characterized by an effective Fano factor of 0.12. The average energy expended per created pair was determined to be 2.95 ±0.02 eV at 90°K.

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