Abstract: This invention describes a nanometer scale interband lateral resonant tunneling transistor, and the method for producing the same, with lateral geometry, good fanout properties and suitable for incorporation into large-scale integrated circuits. The transistor is of a single gate design and operation is based on resonant tunneling processes in narrow-gap nanostructures which are highly responsive to quantum phenomena. Such quantum-effect devices can have very high density, operate at much higher temperatures and are capable of driving other devices.

Abstract: The present invention relates to novel optical devices operating in the infrared, based on indirect narrow-gap superlattices (INGS) as the active optical materials. The novel optical devices include (1) wideband all-optical switches, which combine small insertion loss at low light intensities with efficient optical switching and optical limiting at high intensities, and (2) wideband infrared detectors with high collection efficiency and low tunneling noise currents, suitable for use in longwave infrared focal plane arrays. INGS comprise multiple semimetal/semiconductor layers having compatible crystal symmetry across each heterojunction between a given semimetal and the adjoining semiconductor, wherein each semimetal layer sandwiched between semiconductor layers is grown thin enough that each semimetal layer becomes a semiconductor, and wherein each semiconductor layer is thin enough that there is coupling between adjacent semiconductor layers.

Abstract: A protective layer laser hardens an optical detector. The material for the rotective layer is Hg.sub.1-Y Cd.sub.Y Te, where Y is selected so that the band gap of the protective layer is higher than the expected energy level for photons impinging on the protective layer. Photons with energy levels lower than the band gap are transmitted by the protective layer while photons exceeding the band gap energy level are absorbed or reflected by the protective layer. A semiconductor junction can be formed on the opposite side of the substrate from a Hg.sub.X Cd.sub.X Te layer with a band gap lower than the expected energy level, so that photons transmitted through the substrate are absorbed in the Hg.sub.X Cd.sub.X Te layer and, therefore, detected at the junction. At sufficiently high intensities where detector damage could result, the protective layer switches so that the incident photons are either absorbed or reflected, thus protecting the detector from damage.

Abstract: A bistable optical switch comprising a Fabry-Perot resonator containing a nonlinear semiconductor medium with a desired band structure and whose susceptibility (refractive index) varies with optical energy density. The Fabry-Perot resonator is biased to a point where two stable transmission states are possible. Switching is accomplished by pumping the nonlinear material with an energy hw in the range 1/2.DELTA..sub.g <hw<.DELTA..sub.g, where .DELTA..sub.g is the bandgap between the upper valence band and the conduction band of the nonlinear material, in order to stimulate a two-photon valence-to-conduction band absorption transition at a non-minimum energy and thereby make possible a one-hw photon virtual transition between the heavy hole and split-off valence bands of the nonlinear material. This virtual transition alters the susceptibility thereby switching the resonator to a different stable transmission state.

Abstract: A method for accurately determining the compensation density of n-type naw-gap semiconductors. A semiconductor sample is irradiated with laser pulses of a particular density and pulse width for a particular time length with the sample maintained at a low temperature to generate photo-excited carriers within the semiconductor sample. Photons of energy less than the energy gap, E.sub.g, but greater than, E.sub.g /2, generate carriers uniformly throughout the semiconductor via the nonlinear mechanism of two-photon absorption. Photo-Hall measurements are made on the semiconductor sample during and after the laser pulse to determine the mobility, .mu., and carrier density, n, as a function of time using suitable equipment such as a computer controlled digital processing oscilloscope to display the curves. The curves displayed by the oscilloscope are compared with previously calculated curves to obtain a match and thereby determine the quality of the sample.