Frequency- and Power-Dependent Photoresponse of a Perovskite Photodetector Down to the Single-Photon Level.

Organometallic halide perovskites attract strong interests for their high photoresponsivity and solar cell efficiency. However, there was no systematic study of their power- and frequency-dependent photoresponsivity. We identified two different power-dependent photoresponse types in methylammonium lead iodide perovskite (MAPbI3) photodetectors. In the first type, the photoresponse remains constant from 5 Hz to 800 MHz. In the second type, absorption of a single photon can generate a persistent photoconductivity of 30 pA under an applied electric field of 2.5 × 104 V/cm. Additional absorbed photons, up to 8, linearly increase the persistent photoconductivity, which saturates with the absorption of more than 10 photons. This is different than single-photon avalanche detectors (SPADs) because the single-photon response is persistent as long as the device is under bias, providing unique opportunities for novel electronic and photonic devices such as analogue memories for neuromorphic computing. We propose an avalanche-like process for iodine ions and estimate that absorption of a single 0.38 aJ photon triggers the motion of 108-9 ions, resulting in accumulations of ions and charged vacancies at the MAPbI3/electrode interfaces to cause the band bending and change of electric material properties. We have made the first observation that single-digit photon absorption can alter the macroscopic electric and optoelectronic properties of a perovskite thin film.

Single photon detector with a mesoscopic cycling excitation design of dual gain sections and a transport barrier.

Conventional semiconductor single photon detectors (SPDs) are Geiger-mode avalanche photodiodes made of high-quality crystalline semiconductors and require external quenching circuits. Here we report a design of an SPD having dual gain sections to obtain mesoscopic cycling excitation and an amorphous/crystalline heterointerface to form an electron transport barrier that suppresses gain fluctuations. The dual gain sections comprise a crystalline silicon n/p junction and a thin layer of amorphous silicon. At 100 MHz, the device shows single photon detection efficiency greater than 11%, self-recovery time of less than 1 ns, and an excess noise factor of 1.22 at an average gain around 75,000 under 8.5 V bias.

Complementary metal-oxide-semiconductor compatible 1060 nm photodetector with ultrahigh gain under low bias.

Falling on the tail of the absorption spectrum of silicon, 1060 nm Si detectors often suffer from low responsivity unless an exceedingly thick absorption layer is used, a design that requires high operation voltage and high purity epitaxial or substrate material. We report an all-silicon 1060 nm detector with ultrahigh gain to allow for low operation voltage (<4 V) and thin (200 nm) effective absorption layer, using the recently discovered cycling excitation process. With 1% external quantum efficiency, a responsivity of 93 A/W was demonstrated in a p/n junction device compatible with the complementary metal-oxide-semiconductor process.