Picosecond Avalanche Detector -- working principle and gain measurement with a proof-of-concept prototype

TL;DR

This paper introduces a novel picosecond avalanche detector based on a multi-junction silicon pixel design, demonstrating its working principle and gain measurement through a prototype with promising avalanche gain performance.

Contribution

It presents a new detector architecture and a proof-of-concept prototype, including experimental validation and gain measurement, advancing high-resolution particle tracking technology.

Findings

Prototype achieves avalanche gain up to 23

Device is functional with measurable gain

Space-charge effects limit maximum gain

Abstract

The Picosecond Avalanche Detector is a multi-junction silicon pixel detector based on a $\mathrm{(NP)_{drift}(NP)_{gain}}$ structure, devised to enable charged-particle tracking with high spatial resolution and picosecond time-stamp capability. It uses a continuous junction deep inside the sensor volume to amplify the primary charge produced by ionizing radiation in a thin absorption layer. The signal is then induced by the secondary charges moving inside a thicker drift region. A proof-of-concept monolithic prototype, consisting of a matrix of hexagonal pixels with 100 $\mu$m pitch, has been produced using the 130 nm SiGe BiCMOS process by IHP microelectronics. Measurements on probe station and with a $^{55}$Fe X-ray source show that the prototype is functional and displays avalanche gain up to a maximum electron gain of 23. A study of the avalanche characteristics, corroborated by TCAD simulations, indicates that space-charge effects due to the large primary charge produced by the conversion of X-rays from the $^{55}$Fe source limits the effective gain.