We are developing Germanium Blocked Impurity Band (BIB) detectors using Liquid Phase Epitaxy (LPE) to grow the high purity blocking layer and the heavily doped infrared absorbing layer. The properties of both epilayers require very low structural and electrical defect concentrations. To achieve these stringent demands, we have developed a high purity LPE process which can be used for the growth of high purity as well as purely doped Ge epilayers. We chose a low melting point, high purity metal with negligible solubility in Ge as a solvent. A good candidate is Pb, a group IV element with a solubility <1017 cm3 at 650°C which does not form electronic levels in the band gap of Ge. The Ge single crystal substrates are optically polished and orientated -4-2° away from (111). The first tests with BIB structures with just the purely doped absorbing layer grown on high purity substrates with LPE look very promising. The detectors exhibit extended wavelength cutoffwhen compared to standard Ge:Ga photoconductors (165 m vs. 120 rim) and show the expected asymmetric currentvoltage dependencies. Future work on these devices will include optimizing doping, dark current, layer thickness, absolute responsivity, Noise Equivalent Power (NEP), and even longer wavelength cutoff as well as an indepth understanding of how the parameters are interrelated. Keywords: Germanium, Far Infrared Detectors, Epitaxy

Date Published: 23 October 1997
PDF: 7 pages
Proc. SPIE 3122, Infrared Spaceborne Remote Sensing V, (23 October 1997); doi: 10.1117/12.278999

Published in SPIE Proceedings Vol. 3122:
Infrared Spaceborne Remote Sensing V
Marija Strojnik; Bjorn F. Andresen, Editor(s)