An Overview of CMOS Photodetectors Utilizing Current-Assistance for Swift and Efficient Photo-Carrier Detection

This review paper presents an assortment of research on a family of photodetectors which use the same base mechanism, current assistance, for the operation. Current assistance is used to create a drift field in the semiconductor, more specifically silicon, in order to improve the bandwidth and the quantum efficiency. Based on the detector and application, the drift field can be static or modulated. Applications include 3D imaging (both direct and indirect time-of-flight), optical receivers and fluorescence lifetime imaging. This work discusses the current-assistance principle, the various photodetectors using this principle and a comparison is made with other state-of-the-art photodetectors used for the same application.

High-responsivity graphene photodetectors integrated on silicon microring resonators

Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs’ low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10−9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print.