512- and 1024-element linear InGaAs detector arrays for near-infrared (1-3μm) environmental sensing

512 and 1024 elements linear InxGa1-xAs detector arrays have been fabricated for cutoff wavelengths of 1.7 micrometers (x equals 0.53, Eg equals 0.73 eV), 2.2 micrometers (x equals 0.71, Eg equals 0.56 eV), and 2.6 micrometers (x equals 0.82, Eg equals 0.47 eV) using hydride vapor phase epitaxy (VPE) and metallorganic chemical vapor deposition (MOCVD). The 25 X 500 micrometers s pixel sizes have a center to center spacing of 25 micrometers and currently exhibit typical leakage currents of 6 pA (300 K, -10 mV) for 1.7 micrometers cutoff arrays, 500 pA (300 K, -10 mV) for 2.2 micrometers cutoff arrays, and 20 nA (300 K, -10 mV) for 2.6 micrometers cutoff arrays. Improved crystal growth, n-type sulfur doping (-1 X 1017 cm-3) of the semiconductor 'cap' layer and the active InGaAs layer, and post-crystal growth thermal cyclings of the detector wafers have helped to reduce the leakage current in these detectors. Furthermore, these techniques have produced a remarkable increase in the photodetector yields, which is essential for the commercial viability of these arrays. The relationship between the photodetector bandgap (Eg) and the theoretically lowest attainable leakage current is discussed. The design of a new infrared (IR) multiplexer operating at near zero bias is also discussed.

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