The disclosure relates to a detector of infrared radiation which employs Group III-V compound semiconductor technology and includes a conductive substrate, of a material such as GaAs. Upon this substrate is deposited a lattice structure, including thin alternating layers of a wider and a narrower energy band gap material (AlGaAs and GaAs) periodically disposed. Upon this is deposited a layer of an alloyed semiconductor of moderate bandgap, into which photoexcited carriers are injected, and upon this is deposited a layer of wider bandgap material against which the carriers are trapped and thus collected. The lattice is designed so that the energy gap between the first two bands produced by the periodic structure is equal to the infrared photon energy. The doping is such as to nearly fill the first band with free carriers. Thus infrared radiation is efficiently absorbed, generating free carriers in the second band of the lattice. The bandgap of the next layer is chosen so that these photoexcited carriers may easily pass into this layer, while those in the lower-energy band are blocked. These carriers are propelled across this next layer by an applied electric field and are collected at the interface with a wide-gap layer.
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