# Black-silicon ultraviolet photodiodes achieve external quantum efficiency above 130%

## TL;DR

This paper reports a nanostructured silicon UV photodiode achieving an external quantum efficiency above 130%, surpassing the one photon-one electron limit, with implications for improved UV sensors and beyond.

## Contribution

It introduces a novel silicon photodiode design that exceeds the theoretical efficiency limit through impact ionization in nanostructures.

## Key findings

- External quantum efficiency above 130% achieved
- Effective carrier multiplication via impact ionization demonstrated
- Potential for extending high efficiency to other semiconductor materials

## Abstract

At present, ultraviolet sensors are utilized in numerous fields ranging from various spectroscopy applications via biotechnical innovations to industrial process control. Despite of this, the performance of current UV sensors is surprisingly poor. Here, we break the theoretical one photon - one electron barrier and demonstrate a device with a certified external quantum efficiency (EQE) above 130% in UV range without external amplification. The record high performance is obtained using a nanostructured silicon photodiode with self-induced junction. We show that the high efficiency is based on effective utilization of multiple carrier generation by impact ionization taking place in the nanostructures. While the results can readily have a significant impact on the UV-sensor industry, the underlying technological concept can be applied to other semiconductor materials, thereby extending above unity response to longer wavelengths and offering new perspectives for improving efficiencies beyond the Shockley-Queisser limit.

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Source: https://tomesphere.com/paper/1907.13397