Novel III-V heterostructures and designs for high-performance avalanche photodiode devices

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An avalanche photodiode (APD) is a specialized semiconductor device used for the detection of light and, incertain applications, even individual photons. The APDs are therefore typically used in various applicationsrequiring sensitive detection of light. They have been successfully manufactured for operation at differentwavelengths, for ranging applications, and various light sensing solutions. A common feature of these devicesis a multiplication region: a region of very high electric field strength in which excited photo-current causes acascade of impact ionizations yielding a significantly amplified signal at the anode and cathode. There areseveral applications for APD devices in the wavelength range of 1.5microns. The InP-based epitaxial materialshave been perfected to optimize the APD performance using InGaAs and InP heterostructures. The dopingprofiles have been obtained by combining epitaxial doping and diffusion doping technique in these materials.To expand into new applications it is important to further improve the performance of such III-V APDs andcomplement the available baseline products. Specific areas for improvement are dark currents (bulk andsurface), steeper I-V curve in the avalanche region so the APD can be operated more safely further from thebreakdown voltage, and lower intrinsic noise equivalent power for better signal-to-noise ratio (SNR) whenreceiving ultra-low light levels and enabling further ranging in laser-range finder applications. APDs requireexceptional design and process controls since the electric fields that initiate avalanche gain have very tightrequirements and the interaction of the materials and doping levels of the various layers needed to create a III-VAPD are complex with a narrow range of values that can be expected to yield good performance. This CRDproject will allow the optimization of the APD device performance by designing novel heterostructurestrategies with better optimized AlInAs/InGaAs/InP epilayers and doping designs.