Towards GaAs Thin-Film Tracking Detectors

TL;DR

This paper explores the fabrication and characterization of GaAs thin-film detectors as a promising alternative to silicon for high-energy particle tracking, emphasizing their potential for fast timing and radiation tolerance.

Contribution

It reports on the successful fabrication of n-in-n GaAs thin-film devices with full depletion and assesses their signal collection speed and structural properties, demonstrating their suitability for next-generation detectors.

Findings

GaAs thin films can be fully depleted at 10 μm thickness.

GaAs detectors exhibit fast signal collection speeds.

Structural analysis confirms junction formation and residual doping.

Abstract

Silicon-based tracking detectors have been used in several important applications, such as in cancer therapy using particle beams, and for the discovery of new elementary particles at the Large Hadron Collider at CERN. III-V semiconductor materials are an attractive alternative to silicon for this application, as they have some superior physical properties. They could meet the demands for fast timing detectors allowing time-of-flight measurements with ps resolution while being radiation tolerant and cost-efficient. As a material with a larger density, higher atomic number Z and much higher electron mobility than silicon, GaAs exhibits faster signal collection and a larger signal per {\mu}m of sensor thickness. In this work, we report on the fabrication of n-in-n GaAs thin-film devices intended to serve next-generation high-energy particle tracking detectors. Molecular beam epitaxy (MBE) was used to grow high-quality GaAs films with doping levels sufficiently low to achieve full depletion for detectors with an active thickness of 10 {\mu}m. The signal collection speed of the detector structures was assessed using the transient current technique (TCT). To elucidate the structural properties of the detector, Kelvin probe force microscopy (KPFM) was used, which confirmed the formation of the junction in the detector and revealed residual doping in the intrinsic layer. Our results suggest that GaAs thin films are suitable candidates to achieve thin and radiation-tolerant tracking detectors.