Fabrication and assessment of optically immersed CdHgTe detector arrays

Optical concentration is a means of improving the performance of CdHgTe photodiodes so that they can be used at longer wavelengths and higher temperatures. The authors describe the fabrication of silicon microlens arrays the fabrication of 128*1 arrays of miniature CdHgTe diodes, the mating of these two components, and the assessment of the resulting devices. For a device operating at 77 K and having a cut-off wavelength of 12 mu m the R₀I₀ product is improved by an order of magnitude over a conventional detector. At 192 K and a wavelength of 9 mu m useful peak detectivities of 4*10⁹ cm Hz^1/2 W^-1 are obtained. The lens/diode combination has a field of view of 30 degrees . The photocurrent gain on immersion is 10 to 12 times.