Abstract: A multi-waveband temperature sensor array, in which each superpixel (e.g., 2×2 pixel cell) operates at a distinct thermal infrared (IR) waveband (e.g. four wavebands) is disclosed. Using an example high spatial resolution, four-band thermal IR band photodetector array, accurate temperature measurements on the surface of an object can be made without prior knowledge of the object emissivity. The multiband photodetector may employ intersubband transition in III-V semiconductor-based quantum layered structures where each photodetector stack absorbs photons within the specified wavelength band while allowing the transmission of photons in other spectral bands, thus efficiently permitting multiband detection. This produces multiple, spectrally resolved images of a scene that are recorded simultaneously in a single snapshot of the FPA. From the multispectral images and calibration information about the system, computational algorithms are used to produce the surface temperature map of a target.

Abstract: A quantum well infrared photodetector (QWIP) focal plane array having structures, each structure having stacked layers of quantum wells and a reflective grating to provide polarization sensitivity. The reflective grating is etched to provide electrical contacts for individual pixels. The reflective gratings comprise grooves, where the grooves for a particular structure run in a particular direction to provide polarization sensitivity. Each structure may comprise groups of quantum well layers, each group sensitive to a particular frequency band. By shorting out unwanted quantum well layers, and by forming the reflective gratings to come into contact with the quantum well layers having a particular frequency band sensitivity, the pixels in the QWIP focal plane array may provide frequency and polarization information.

Abstract: Quantum-well sensors having an array of spatially separated quantum-well columns formed on a substrate. A grating can be formed increase the coupling efficiency.

Abstract: Devices and techniques for coupling radiation to intraband quantum-well semiconductor sensors that are insensitive to the wavelength of the coupled radiation. At least one reflective surface is implemented in the quantum-well region to direct incident radiation towards the quantum-well layers.

Abstract: An AlxGa1−xAs/GaAs/AlxGa1−xAs quantum well exhibiting a bound-to-quasibound intersubband absorptive transition is described. The bound-to-quasibound transition exists when the first excited state has the same energy as the “top” (i.e., the upper-most energy barrier) of the quantum well. The energy barrier for thermionic emission is thus equal to the energy required for intersubband absorption. Increasing the energy barrier in this way reduces dark current. The amount of photocurrent generated by the quantum well is maintained at a high level.

Abstract: Device designs and techniques for reducing the dark current in quantum-well detectors.

Abstract: An AlxGa1−xAs/GaAs/AlxGa1−xAs quantum well exhibiting a bound-to-quasibound intersubband absorptive transition is described. The bound-to-quasibound transition exists when the first excited state has the same energy as the “top” (i.e., the upper-most energy barrier) of the quantum well. The energy barrier for thermionic emission is thus equal to the energy required for intersubband absorption. Increasing the energy barrier in this way reduces dark current. The amount of photocurrent generated by the quantum well is maintained at a high level.

Abstract: Devices and techniques for coupling radiation to intraband quantum-well semiconductor sensors that are insensitive to the wavelength of the coupled radiation. At least one reflective surface is implemented in the quantum-well region to direct incident radiation towards the quantum-well layers.

Abstract: Device designs and techniques for forming multiple-band quantum-well detectors.

Abstract: Devices and techniques for coupling radiation to intraband quantum-well semiconductor sensors that are insensitive to the wavelength of the coupled radiation. At least one reflective surface is implemented in the quantum-well region to direct incident radiation towards the quantum-well layers.

Abstract: A three-color QWIP focal plane array is based on a GaAs/AlGaAs material system. Three-color QWIPs enable target recognition and discriminating systems to precisely obtain the temperature of two objects in the presence of a third unknown parameter. The QWIPs are designed to reduce the normal reflection over a significant wavelength range. One aspect of the present invention involves two photon absorptions per transition in a double quantum well structure which is different from typical QWIP structures. This design is expected to significantly reduce the dark current as a result of higher thermionic barriers and therefore allow the devices to operate at elevated temperatures. The device is expected to be fabricate using a GaAs/AlxGa1−xAs material system on a semi-insulating GaAs substrate by Molecular Beam Epitacy (MBE).

Abstract: Device designs and techniques for forming multiple-band quantum-well detectors.

Abstract: Techniques for coupling radiation into a quantum-well detector by using a two-dimensional array of grating cells to form at least three different grating directions to provide efficient coupling.

Abstract: Device designs and techniques for reducing the dark current in quantum-well detectors.

Abstract: Quantum-well sensors having an array of spatially separated quantum-well columns formed on a substrate. A grating can be formed increase the coupling efficiency.

Abstract: Quantum-well sensors having an array of spatially separated quantum-well columns formed on a substrate. A grating can be formed increase the coupling efficiency.

Abstract: An AlxGa1−xAs/GaAs/AlxGa1−xAs quantum well exhibiting a bound-to-quasibound intersubband absorptive transition is described. The bound-to-quasibound transition exists when the first excited state has the same energy as the “top” (i.e., the upper-most energy barrier) of the quantum well. The energy barrier for thermionic emission is thus equal to the energy required for intersubband absorption. Increasing the energy barrier in this way reduces dark current. The amount of photocurrent generated by the quantum well is maintained at a high level.

Abstract: Quantum-well sensing arrays for detecting radiation with two or more wavelengths. Each pixel includes at least two different quantum-well sensing stacks that are biased at a common voltage.

Abstract: For the growth of strain-layer materials and high quality single and multiple quantum wells, the instantaneous control of growth front stoichiometry is critical. The process of the invention adjusts the offset or phase of MBE control shutters to program the instantaneous arrival or flux rate of In and As.sub.4 reactants to grow InAs. The interrupted growth of first In, then As.sub.4, is also a key feature.

Abstract: III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group II and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation to low temperature, and to permit the film to relax to equilibrium. The method of the invention 1) minimizes starting step density on sample surface; 2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 mono-layers at a time); 3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and 4) uses time-resolved RHEED to achieve aspects (1)-14 (3).