# Local avalanche photodetectors driven by lightning-rod effect and surface plasmon excitations

## TL;DR

This paper introduces a new design for ultraviolet avalanche photodetectors that improves performance and reduces breakdown voltage using micro-holes and nano-triangles.

## Contribution

The novel integration of lightning-rod effect and surface plasmon excitations in APD design significantly lowers breakdown voltage.

## Key findings

- The device achieves an avalanche breakdown voltage of ~14.5 V, a tenfold reduction compared to conventional APDs.
- It demonstrates a detectivity of 2 × 10¹³ Jones and nanosecond-level response time without a quenching circuit.
- The design enables stable detection through localized field enhancement using micro-holes and Al nano-triangles.

## Abstract

Sensitive avalanche photodetectors (APDs) that operate within the ultraviolet spectrum are critically required for applications in detecting fire and deep-space exploration. However, the development of such devices faces significant challenges, including high avalanche breakdown voltage, the necessity for complex quenching circuits, and thermal runaway associated with Geiger-mode avalanche operation. To mitigate these issues, we report on a 4H-SiC APD design utilizing micro-holes (MHs) structures and Al nano-triangles (NTs) to enhance surface electric field driven by strong localized surface plasmon excitations and lightning-rod effect. The device demonstrates a low avalanche breakdown voltage of approximately 14.5 V, a high detectivity of 2 × 1013 Jones, a nanosecond-level response time, and repeated stable detections without the requirement of a quenching circuit. Collectively, when compared with the conventional wide-bandgap-based APDs, this device achieves a reduction in avalanche breakdown voltage by an order of magnitude. Consequently, the proposed APD configuration presents a promising candidate for ultraviolet detection and integrated optoelectronic circuits.

This study presents an approach to enhancing the local field of avalanche photodetectors by integrating the lightning-rod effect with localized surface plasmon excitations.