Photo-Induced Current Amplification and Intrinsic Frequency Mixing for next-generation range finders, 3D image sensors and systems - PICASSO

• Applicant: Privatdozent Dr.-Ing. Andreas Bablich, Ph.D.
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 561870720

The aim of this project is to investigate the fundamental performance potential and performance limits of nonlinear IPD sensors (IPD = Intrinsic Photomixing Detector) based on amorphous silicon (a-Si:H) and amorphous silicon alloys (amorphous silicon germanium and silicon carbide) for highly integrated and high-precision rangefinders and 3D camera systems based on the time-of-flight principle. In addition to the development of component-specific models and simulations, the technological implementation of innovative IPD sensors will be developed. IPD single pixels based on the developed models will be demonstrated experimentally and the basic physical understanding developed will be validated and used for recursive optimization of the concepts. Various component architectures and material compositions will be investigated to I.) maximize the cut-off frequency and thus achievable depth resolutions, II.) demonstrate robust and precise distance ranging/3D scene detection even with lat low-light levels and extensive stray-light and III.) demonstrate maximum sensitivities (detection limits) of the IPD concept in the infrared spectral range for eye-safe applicability and a wide range of applications. Current Time-of-Flight sensors suffer from significant drawbacks in terms of achievable integration/pixel densities and are not suitable for high-precision and, at the same time, highly integrated 3D imaging at their current stage. The technological basis of the a-Si:H IPD offers the possibility of direct CMOS-compatible Back-End-of-Line integration and thus the potential for a massive increase in pixel density and depth resolution. To realize this, a comprehensive physical understanding of different amorphous IPD sensor concepts will be developed as part of the PICASSO project. This requires the modelling and development of optimized component concepts based on a well-founded material database, which is built up metrologically from electro-optical thin-film characterizations and complementary nanoanalytical methods. The project also includes the establishment of semiconductor process chains for manufacturing the sensors and the development of the necessary measurement environments for application-specific distance/3D scene detection. Besides performance benefits of the sensor concept compared to the state-of-the-art (massive increase in spectral sensitivity through electro-optical gating, better depth resolution and measurement accuracy), the planned a-Si:H technology platform also offers significant advantages, as it enables maximum scalability (geometric fill factors of up to 100 %), technology compatibility (low-temperature PECVD process) and adaptability to specific distance measurement requirements (precise adjustability of spectral sensitivity through bandgap engineering/alloys).

• DFG Programme: Research Grants