In this chapter the following materials systems will be evaluated and compared as potential IR photon detectors, utilizing the normalized thermal generation rate parameter discussed in Chapter 2 as the performance differentiator: 1. Intrinsic direct bandgap semiconductors, 2. Extrinsic semiconductors, 3. IR quantum wells (QWIPs), 4. Silicon Schottky barriers, and 5. High-temperature superconductors.
This comparison will concentrate on the two spectral bands of prime importance to tactical IR systems, that is, the atmospheric transmission windows at 3-5 µm and 8-12 µm. The list is not meant to be exhaustive, but it does represent the primary materials candidates in vogue at the present time. It should be emphasized that any materials system proposed in the future for potential IR detection purposes, such as Type II superlattices, could also be easily compared to the current group by a simple consideration of its thermal generation rate, provided values of the relevant carrier concentration and lifetime as a function of temperature, together with the absorption quantum efficiency, are known. The high-temperature superconductor is a particularly interesting case, and it is included in the above list because it illustrates the enabling power of this modeling technique and provides a realistic estimate of potential detector performance without any expenditure of significant experimental resources.
Online access to SPIE eBooks is limited to subscribing institutions.