Nanoscale Single-Photon Detectors

Abstract

Photodetectors are universal sensors employed in telecommunication technologies, telescopes for astronomy, optical imaging, environmental monitoring, and spectroscopy. The Avalanche Photodiode (APD) is widely used in these areas due to its CMOS integration and high sensitivities in linear operation. Demand for higher sensitivity detectors has steadily increased as technology has improved, with many fields requiring low light and single photon detection levels, such as quantum communications. APDs can achieve single photon sensitivities. However they require very high bias (100 -300 V) to operate. In lab environments and special use equipment superconducting single photon nanowire detectors have been employed for their high detection efficiencies, though their cryogenic cooling makes them bulky and inconvenient. A new CMOS compatible detector based on the cycling excitation process (CEP) has demonstrated improved performance from APDs with 30 dB of photocurrent gain and excess noise factors (ENF) of 2 at room temperature operations. Fabrication process flows are developed and employed to create CEP detectors that demonstrate a responsivity greater than 1 in linear operation at 14 V operating bias and gain equivalent to previous works in both DC and AC operation. Low light and single photon signals suffer disproportionately from optical losses, where losses from reflected light, unabsorbed light, and non-ideal absorption make up a significant proportion of detection events. Solar cell technology has developed several approaches to achieve high optical efficiencies, such as antireflection coatings, photonic crystals (PC) and plasmonics. PCs have high flexibility in their design parameters and are easily configurable to desired wavelengths, making them an appealing solution. In this work, we propose and simulate different photonic crystal (PC) structures to enhance the optical efficiency of CEP detectors and develop fabrication process flows to realise them.