Novel design paradigm for highly efficient and low noise photodetectors

Abstract Achieving high quantum efficiency (QE) with low dark count is essential for highly sensitive photodetectors (PDs), including single photon avalanche detectors (SPAD). However, high QE requires a thicker absorber region, which leads to high dark current and noise, which in turn affects PD’s detectivity and SPADs’ photodetection efficiency and dark count. The holy grail of PD and avalanche photodiode designs is to achieve the highest QE with the thinnest absorber and still enable large avalanche gain as needed. We have developed a new design paradigm that exploits the coupling between dielectric Mie resonance and transverse propagating modes in thin layers. The Mie resonance efficiently launches the incident light at an angle in an ultra-thin absorber, and when coupled to transverse waves, the light propagates laterally and is fully absorbed owing to the longer optical path. Consequently, with the appropriate choice of materials for a chosen wavelength, a high absorption (∼90%) within typically <100 nm-thick absorber is possible. For illustration, we apply our approach to design a Si-based detector operating at 810 nm and an InGaAs-based detector operating at 1550 nm and predict that the dark current at room temperature will be reduced at least by two orders of magnitude. In addition, the lateral distances between contacts are often in a few microns, enabling these designs for large avalanching gain.