9B3 - Semiconductor lasers and fast detectors in the infrared (3 to 15 microns)

Small energy gap semiconductors such as InAs, InSb, and Hg
1-x
Cd
x
Te (where
0.15 \leq x \leq 0.40
) allow one to build infrared coherent emitters and fast detectors in a wide wavelength range where practical applications are anticipated (3 to 15 microns, approximately). Some recent achievements of these devices are presented. Previously described indium arsenide junction lasers have been improved. Continuous emission is obtained at 27°K, at a level of 20 mW. Relaxation oscillations of the emitted coherent radiation have been observed at a frequency of 20 Mc/s. Sub-laser emission has been observed at 3 microns on HgTe-CdTe alloy
p-n
junction. Coherent emission can be predicted on the basis of the band structure. The intrinsic detectors are faster and can work at higher temperatures than impurity photoconductors. Besides photovoltaic InAs and InSb detectors, we have developed three types of Hg
1-x
Cd
x
Te detectors for the 3 to 12 microns wavelength range: photovoltaic, photoconductive cells, and graded band-gap structures. Theoretical possibilities of this type are discussed and preliminary experimental results for all three are given. For a photoconductive cell whose response peaks at 10 microns a time constant of 70 ns has been measured using an InAs laser as a source.