Semiconductor gamma ray detector including compositionally grade

Details Semiconductor gamma ray detector including compositionally grade Semiconductor gamma ray detector including compositionally grade

1993-06-11

1995-02-21

Hannaher, Constantine

Radiant energy

Invisible radiant energy responsive electric signalling

Semiconductor system

25037012, 25037014, 267188, 267189, 267191, H01L 31105, H01L 310304, H01L 310296

Patent

active

053918827

ABSTRACT:
A P-type/intrinsic/N-type (P-I-N) gamma ray detector (10) includes a semiconductor detector layer (12) of intrinsic cadmium telluride (CdTe) or cadmium zinc telluride (CdZnTe). P- and N-doped semiconductor layers (14,16) of mercury cadmium telluride (HgCdTe) are formed on the opposite surfaces (12a,12b) of the detector layer (12), and ohmic metal contacts (18,20) are formed on the doped layers (14,16). The composition of the doped layers (14,16) is Hg.sub.1-x Cd.sub.x Te, and is graded such that x progressively decreases with distance from the detector layer (12) toward the ohmic contacts (18,20). This causes the bandgap of the doped layers (14,16) to also decrease from the detector layer (12) toward the ohmic contacts (18,20), forming potential barriers (E1,E2) which block leakage currents constituted by injection of minority carriers from the ohmic contacts (18,20) into the detector layer (12) and provide low resistance between the doped layers (14,16) and ohmic contacts (18,20). The detector layer (12) and doped layers (14,16) are annealed during fabrication, causing diffusion of mercury from the doped layers (14,16) into the detector layer (12) and diffusion of cadmium from the detector layer (12) into the doped layers (14,16), thereby increasing the heights of the potential barriers (E1,E2).

REFERENCES:
patent: 4801984 (1989-01-01), Woodall
patent: 5162891 (1992-11-01), Burroughes et al.
Hazlett, T. et al., "Large, High Resolution CdTe Gamma Ray Sensors", IEEE Transactions on Nuclear Science, vol. 33, No. 1, Feb. 1986, pp. 332-335.
Ryan, F. et al., "Gamma Ray Detectors with HgCdTe Contact Layers", Applied Physics Letters, vol. 46, No. 3, Feb. 1985, pp. 274-276.

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