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Heterostructures which utilize a thin film of narrow-gap semiconductor deposited on a p-Si substrate have the potential to function as high-efficiency, easily fabricated infrared detectors. We have characterized two such systems, namely PbTe and SnTe. The structures were prepared by congruently evaporating films of PbTe and SnTe from single sources of the compounds onto 〈100〉 p-Si wafers which were chemically cleaned prior to deposition. We have analyzed the composition and electrical properties of the deposited films, as well as the electrical and photoresponse properties of the heterostructures. Current–voltage measurements indicated rectifying behavior with good ideality factor and low leakage down to 77 K for the case of SnTe/Si. High series resistance of the PbTe/Si structures made electrical characterization difficult, though they also showed rectifying behavior and low reverse leakage. Photoresponse measurements indicate a threshold of 0.36–0.4 eV for SnTe/p-Si and 0.3 eV for PbTe/p-Si. These results indicate that the PbSnTe alloy on p-Si will have a lower energy threshold than either of the binary compounds.

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We propose a novel device concept for infrared detectors which utilizes a thin film of a narrow gap semiconductor deposited on a p-Si substrate. Such a device would retain the advantages of using a Si-based technology, while operating with higher quantum efficiency. The operation of the device would be similar to a Schottky barrier detector, in that carriers would be excited from the overlayer into the substrate. However, the absence of undesired states near the Fermi level should lead to more efficient generation and transport of photoexcited carriers. Calculations using a recently developed diffusion model for the behavior of Schottky barrier detectors indicate the potential for an order of magnitude improvement in quantum efficiency over PtSi/p-Si detectors at a wavelength of 4 μm.