Extended InGaAs on GaAs detectors for SWIR linear sensors

摘要

High quality extended-wavelength InGaAs (80% In) has been grown hetero-epitaxially on 3"-GaAs substrates by means of Molecular Beam Epitaxy (MBE). In contrast growth on InP, sensor manufacturing on GaAs substrates can be readily scaled to 6". An additional benefit is the larger cut-off of the 80%-In material (2.5μm vs. l.7μm). The photodiode layer design was optimized for maximum improvement of dark current with temperature. A high-uniformity and high-yield process was developed to manufacture bondable 128 pixel 50 μm pitch linear array sensors. To this end, a dedicated mesa-type process was developed assuring high uniformity in dark current and photoresponse. The sensors were designed for top-illumination. Sensors have been characterized electrically and optically at the intended thermo-electrical operation temperature (250K). The homogeneity of dark current and photo response was also evaluated at 250K. The improvement in dark current as a function of temperature has been studied in more detail, yielding a zero bias resistance of approximately 2.5 MΩcm{sup}2at 77K. A linear array has been bonded to a commercial CMOS read-out circuit and the functionality is shown. The sensor is suitable for spectroscopic and imaging applications in the short wavelength infrared (SWIR) region. Work is underway to develop sensors with smaller pitch and up to 512 pixels.