High performance Ge: Ga arrays for the far infrared

We report on progress in the construction of highly sensitive arrays of germanium photoconductors for operation at wavelengths between 40 to 120 jim. This technology is being developed for future astronomical missions in the far infrared such as SIRTF. We are evaluating construction techniques that will allow us to build 32x32 format arrays that are reliable and suitable to be qualified for space flight, while retaining the excellent performance of a prototype we have built and tested previously. We review the technical issues in constructing large format far infrared arrays, along with a description of the approaches that have been adopted in the prototype array to deal with these issues. We report on the development of two advanced methods to interconnect the detectors and readouts, that allow the extension of the Z-Plane concept to larger formats: 1.) Flex cable and 2.) tape automated bonding. Both methods are being evaluated in a detailed series of laboratory experiments, including the electrical performance of the integrated readout/interconnect systems, thermal performance, ease of assembly of completed arrays, and mechanical ruggedness. These approaches will be discussed in terms of their use both with readouts that need to operate at temperatures above those acceptable for the detectors (~20K) and with readouts that can operate close to the detector temperature (~2K).