SBIR Phase II: Strained Layer Avalanche Photodiodes for Long Wavelength Applications

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*** 9629778 Olsen This Small Business Innovation Research Phase II project will design, optimize, and deliver a high-performance avalanche photodiode (APD) for use in the 1.0-2.2 um spectral region as a high performance telecommunications and LIDAR receiver. Strained epitaxial layers will be combined with multi-quantum-well (MQW) InGaAsP/InP layers. The strained layer distorts the valence band of the multiplying (gain) region to reduce the field at which ionization occurs. This reduces device operating voltage and also decreases the ratio of hole/electron ionization coefficients (compared to the unstrained case), and thus decreases noise. In Phase I devices were fabricated and tested with tensile and compressive strain. Feasibility of concept was conclusively demonstrated with measured avalanche gains 100 and hole/electron gain ratios of 0.2-0.4. Phase II will fabricate and optimize a reliable planar structure for light response out to 1.65 um which realizes the advantages of low voltage (10-20v), low noise operation, high gain (50) and high yield. These concepts will then be applied to the InAsP/InGaAs materials system, along with the use of ternary InAsP substrates, to achieve low-noise avalanche gain at 2.2um. The project will result in a high performance, low cost, infrared detector for fiber optic communications, eye-safe range-finding and spectroscopy. This device would also be viable for wavelengths beyond 2 um which would open up other commercial possibilities such as gas sensing and windshear detection. APDs are not yet widely used in commercial long-wavelength fiber optic communication systems because of their high-noise properties. Successful completion of a Phase II program would enable commercialization of a low-noise device which would open up a market, presently estimated at over $50 million per year. ***