High Efficiency, Large-area, 1550 nm InGaAs Photodiodes

A stable, well characterized InGaAs materials growth and photodetector fabrication process will be used to fabricate matched photodiodes optimized for balanced homodyne detection. The 1-mm-diameter p-i-n photodetectors will be manufactured back-illuminated with a 5-micron absorber, allowing residual light to reflect off the front-side metal to make a double pass through the active layer. Ultra-high-purity InGaAs will be used so that the absorber can operate fully depleted at relatively low operating voltages (< -5 VDC). The ultra-pure InGaAs will also reduce variation across the 1-mm-diameter detector and prevent breakdown. Operating the detector fully depleted will decrease the carrier transport time and therefore reduce carrier recombination; it will also reduce the detector¿s capacitance. So that stray capacitance is minimized, the detectors will be bump-bonded directly to a sub-mount; the detector will then be integrated with low-noise transimpedance amplifiers and integrated with a three-stage thermoelectric cooler in a hermetic TO-5 package. The matched detectors will be testing and characterized in an optical homodyne detection system.