Semiconductor exhaustion range

If the donors and acceptors are present in equal numbers, the material is said to be a compensated semiconductor. At 0 K these materials are insulators, and it is difficult in practice to distinguish between compensated and intrinsic semiconductors. When all of the impurities are fully ionized so that either all the donor levels have lost an electron or all the acceptor levels have gained an electron, the exhaustion range has been reached. 

Infrared emissions are dependent on the nature of the emissive body and its temperature. For example, a jetfighter emits strongly in the infrared around the wavelength ranges of 2 pm and 3-5 pm from the exhaust nozzle, 4—5 pm from the exhaust gases, and 3-5 pm and 8-12 pm from the flight body. Infrared sensors used in the aforementioned atmospheric windows are semiconductors composed of the chemical compounds PbS for 2.5 pm, InSb for 3-5 pm, and HgCdTe for 3-5 pm and 10 pm. 

---