Experimental Results on Excluded Nonequilibrium Photodetectors

Exclusion of minority carriers in narrow-bandgap semiconductors was demonstrated in a temperature range of 180-295 K, exclusively in the middle wavelength infrared range, i.e., in the range (3-5) pm. Most of the reported experiments were performed on v-type semiconductors [243]. 

Ashley et al. [333] fabricated a number of exclusion structures in mercury cadmium telluride with compositions ranging from 0.23 to 0.30 and for various cutoff wavelengths. A typical structure was 2 mm long, 0.1 mm wide, and 4-8 pm thick. Highly doped n zone was usually formed by ion implantation, with a typical doping level of 5 x lO cm . The active area was passivated by zinc sulfide that 

3 Charge Carrier Management (Thermal Noise Engineering) 

Djuric et al. [358] fabricated InSb-based exclusion structures with light signal arriving through the n zone, rather than laterally as in the quoted structures of Ashley et al. [333]. The highly doped region was formed by implantation of tellurium, with a thickness of (5-10) pm. The level of the v-substrate doping was lO cm. An exclusion threshold current of 270 A/cm was measured and the maximum temperature with measurable exclusion effects was 220 K. 

If the readouts from both of the contact pairs are lead to separate preamplifiers, brought into counterphase and lead to an addition circuit, pink noise will be removed, since it is correlated on both channels, but the signal will remain, since it exists on only one of the contacts. 

---