Ultra-sensitive nonlinear amorphous silicon photodetectors for futures 3D imaging applications (ULTRA-SENSE 3D)

• Applicants: Dr.-Ing. Andreas Bablich, Ph.D.; Professor Dr.-Ing. Peter Haring Bolívar
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512532998

The goal of this project is to explore fundamental potentials and limitations of nonlinear FIP-photodetectors (FIP = Focus-Induced Photoresponse) based on hydrogenated amorphous silicon (a-Si:H) and its alloys for the development of highly integrated 3D camera systems. The project addresses the development of suitable device modeling routines and simulations, the establishment of appropriate semiconductor process technologies to manufacture high performance 3D sensors based on amorphous silicon and its alloys and the experimental demonstration of nonlinear single pixel photodiodes and -arrays for 3D imaging. In this context, different device architectures will be developed. Optimized FIP detector designs will enable 1.) maximum electrical bandwidth and operation frequencies to maximize signal-to-noise ratios (reduction 1/f noise), 2.) maximum responsivities (detection limits) to demonstrate a reliable and robust 3D scene detection at ultra-low light levels, and 3.) optimized depth resolutions achieved by a systematic defect- and field engineering. State-of-the-art FIP concepts obtain significant drawbacks and avoid a fast, high-sensitive 3D scene detection with high depth resolutions. Fundamental goals of this project are: 1.) to develop a detailed physical understanding of the nonlinear, irradiance dependent FIP-effect in a-Si:H based photodetectors, 2.) to systematically investigate fundamental potentials of nonlinear effects in this material system based on the developed physical understanding, appropriate device modeling and simulations, 3.) the demonstration of a high responsivity infrared FIP detector based on a-Si:H and its alloys, and 4.) to demonstrate highly sensitive 3D measurements and to explore fundamental performance limits for 3D imaging based on nonlinear a-Si:H FIP sensors and sensor arrays. The superior goal of this project is to develop, fabricate and demonstrate nonlinear 3D single pixel detectors and a 100-pixel FIP line array that enable to acquire 3D information at high speed, high depth, and spatial resolutions at low irradiances in that material system for the first time. Investigating this new principle thoroughly and to demonstrate 3D scene detection based on the nonlinear FIP, electro-optical simulations and optimized sensor design concepts must be developed prior to the establishment of optimized semiconductor technology process chains and suitable measurement setups. Besides significant performance enhancements (detectivity, depth resolution and speed of operation), the simple FIP device architecture and mature a-Si:H technology platform allow for low-cost 3D sensor fabrication for application specific purposes, scalability and simple device integration on top of electronics with fill factors of 100 %. A further development towards megapixel 3D camera systems shall follow in close cooperation with industrial networks and further projects based on the results achieved in this fundamental, basic research project.

• DFG Programme: Research Grants