Müller, Maurice
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Publication Access status: Metadata only , Graphene-Based Optoelectronic Mixer Device for Time-of-Flight Distance Measurements for Enhanced 3D Imaging ApplicationsA large and growing number of applications benefit from innovative and powerful 3D image sensors. Graphene photodetectors can achieve 3D sensing functionalities by intrinsic optoelectronic frequency mixing due to the nonlinear output characteristics of the sensor. In first proof of principle distance measurement demonstrations, we achieve modulation frequencies of 3.1 MHz, signal-to-noise ratios of ∼40 dB, distance detection up to at least 1 m, and a mean accuracy of 25.6 mm. The scalable More than Moore detector approach enables geometrical fill factors close to 100% and can easily complement powerful functionalities by simple back-end integration on top of CMOS electronics.Source Type:Article - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , High Responsivity and Ultra-Low Detection Limits in Nonlinear a-Si:H p-i-n Photodiodes Enabled by PhotogatingPhotodetectors operating at the wavelength in the visible spectrum are key components in high-performance optoelectronic systems. In this work, massive nonlinearities in amorphous silicon p-i-n photodiodes enabled by the photogating are presented, resulting in responsivities up to 744 mA/W at blue wavelengths. The detectors exhibit significant responsivity gains at optical modulation frequencies exceeding MHz and a more than 60-fold enhanced spectral response compared to the non-gated state. The detection limits down to 10.4 nW/mm 2 and mean signal-to-noise ratio enhancements of 8.5 dB are demonstrated by illuminating the sensor with an additional 6.6 µW/mm 2 red wavelength. Electro-optical simulations verify photocarrier modulation due to defect-induced field screening to be the origin of such high responsivity gains. The experimental results validate the theory and enable the development of commercially viable and complementary metal oxide semiconductor (CMOS) compatible high responsivity photodetectors operating in the visible range for low-light level imaging and detection.Source Type:Article6 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Nonlinear Amorphous Silicon Photodetectors for Distance Ranging(2026)Imaging is a leading instrumentation technique for a vast range of applications. Among others, it is used for scene recognition in autonomous driving, robotics, the medical sector and in smartphones. Besides classical color imaging of two-dimensional (2D) planes, precise and accurate distance ranging is one advancing imaging modality, expanding imaging towards three dimensional (3D) depth sensing. Beyond image quality, high density integration of these image sensors into miniaturized systems, even on a single chip, is a major driver of ongoing development. State-of-the-art distance ranging and 3D imaging techniques are Time-of-Flight (ToF) and Triangulation. Both techniques face challenges in terms of small scale integration capabilities. Typical triangulation-based systems require a specific baseline distance in the cm-range, which is not suitable for monolithic chip integration. ToF-systems can be integrated on a single chip, but its principle requires high precision timings in the sub-ns range, advanced beam steering or complex circuity. Here, developments and achievements on photodetectors based on hydrogenated amorphous silicon (a-Si:H) capable for distance ranging and future 3D imaging are presented. The a-Si:H manufacturing technology at temperatures < 300°C is compatible with the standard CMOS. This approach enables the integration of sensors directly on top of a chip in the back end of line with high geometrical fill factors. The distance ranging operation exploits the nonlinear device behavior with respect to the optical excitation scenario. Based on simulations and subsequent experimental validations, two nonlinear mechanisms and their respective physics are systematically investigated, analyzed and developed towards individual distance ranging techniques. The a-Si:H Focus-Induced Photoresponse (FIP) measures nonlinear current response variations originating from an amplitude-modulated monochromatic optical excitation. The distance is acquired by a frequency selective readout of the nonlinear, focus-dependent sensor signal. Distance resolutions down to 540 μm are achieved, allowing for precise ranging at low measurement and integration effort. The a-Si:H Intrinsic Photomixing Detector (IPD), utilizes an envelope mixing process of two amplitude modulated optical excitations. Thereby, the Time-of-Flight information is transferred to a lower frequency domain, enabling a read-out. This mixing takes place intrinsically within the detector and decreases the measurement complexity. Distance measurements are shown at > 70 m with depth resolutions down to 23 mm, which is comparable with commercial systems. Developments on advanced device concepts are studied and discussed. These concepts systematically improve the sensitivity, spectral bandwidth and speed of the detectors.Source Type:Doctoral ThesisSeries:Höchstfrequenztechnik und QuantenelektronikVolume number:131 823