Cavity Enhanced Tellurium Photodetectors

<b> The proliferation of integrated photonics has led to the widespread adoption of non-silicon material platforms, which can offer wider transparency windows, lower loss, and a diversity of optical nonlinearities. While these platforms have enabled a host of new applications, many still lack one of the building blocks of integrated photonic systems — on-chip photodetectors — and must rely on external detection, hybrid integration, or chip die-bonding. 2D material based photodetectors have shown great promise for both ultra wide-band absorption spectra and easy integration, but the manual processes needed to manufacture flake-based devices have not yet developed to a point where they can be widely adopted for use. Here we show that tellurium (Te), a quasi-2D semi-conductive element, can be evaporated at low temperature directly onto photonic chips to form air-stable, high-responsivity, high-speed, ultrawide-band photodetectors. We demonstrate high responsivity at low-frequencies at visible, telecom and mid-infrared wavelengths, and high-speed telecom operation.</b><br/><b> As we can fabricate these detectors directly on top of existing photonic structures, we can co-design the photonics and detectors in order to optimize their performance. </b><b>We demonstrate this co-design by resonantly enhancing the absorption of a small-volume photodetector with an integrated Fabry-Perot cavity. As these detectors are operating in photoconductive mode, the dark current can add significant noise, so shrinking the detector while maintaining a similar level of absorption increases the signal to noise ratio. Here, we are able to resonantly enhance the absorption by more than an order of magnitude with a comparable reduction in dark current.</b>