California Institute of Technology

The United States of America As Represented by the Administrator

Albert W Overhauser

Joseph Maserjian

A far infrared (FIR) range responsive photodetector. There is a substrate (28) of degenerate germanium. A a plurality of alternating impurity-band (32) and high resistivity (30) layers of germanium are disposed on the substrate (28). The impurity-band layers (32) have a doping concentration therein sufficiently high to include donor bands which can release electrons upon impingement by FIR photons of energy hv greater than an energy gap .epsilon.. The high resistivity layers (30) have a doping concentration therein sufficiently low as to not include conducting donor bands and are depleted of electrons. Metal contacts (36, 38) are provided for applying an electrical field across the substrate (28) and the plurality of layers (30, 32). In the preferred embodiment as shown, the substrate (28) is degenerate n-type (n.sup.++) germanium; the impurity-band layers (32) are n.sup.+ layers of germanium doped to approximately the low 10.sup.16 cm.sup.-3 range; and, the high resistivity layers (30) are n.sup.- layers of germanium doped to a maximum of approximately 10.sup.15 cm.sup.-3. Additionally, the impurity-band layers (32) have a thickness less than a conduction-electron diffusion length in germanium and likely to bein the range of 0.1-1.0 micron, the plurality of impurity-bands (33) is of a number such that the flux of FIR photons (20) passing therethrough will be substantially totally absorbed therein, the thickness of the high resistivity layers (30) is such compared to the voltage applied that the voltage drop in each the high resistivity layers (30) controls the occurance of impact ionization in the impurity-band layers (32) to a desired level.

Alternating gradient photodetector

Semiconductor devices, such as silicon-base MOS devices (10) and solar cells (50), degrade as a result of a variety of reasons, such as hot carriers, photons, and ionizing radiations. Degradation in such devices is cured by the presence of atomic hydrogen. Presently, such devices are exposed to atomic hydrogen during processing. However, a source of atomic hydrogen is not available to heal damage over the lifetime of the device. In accordance with the invention, a source (34, 60) of atomic hydrogen is provided in cooperative relationship with the devices. In a preferred embodiment, the source comprises a layer of palladium, disposed at an appropriate location. The palladium is charged with atomic hydrogen during packaging or encapsulating by exposure to a hydrogen-containing species. The palladium cracks the species to generate atomic hydrogen, which it stores and provides to the device on a real-time basis.

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West Lafayette, IN, United States of America

Albert W Overhauser