Cryogenic Scintillation Properties of n-Type GaAs for the Direct Detection of MeV/c2 Dark Matter

TL;DR

This study explores n-type GaAs as a novel cryogenic scintillation detector for detecting low-mass dark matter particles, demonstrating promising optical properties and low afterglow at cryogenic temperatures.

Contribution

First report of n-type GaAs used as a cryogenic scintillation detector for MeV/c2 dark matter detection, highlighting its optical properties and low afterglow.

Findings

GaAs exhibits emission at 930 nm and excitation at 860 nm.

X-ray excited luminosity ranges from 7 to 43 photons/keV.

No metastable radiative states or afterglow observed.

Abstract

This paper is the first report of n-type GaAs as a cryogenic scintillation radiation detector for the detection of electron recoils from interacting dark matter (DM) particles in the poorly explored MeV/c2 mass range. Seven GaAs samples from two commercial suppliers and with different silicon and boron concentrations were studied for their low temperature optical and scintillation properties. All samples are n-type even at low temperatures and exhibit emission between silicon donors and boron acceptors that peaks at 1.33 eV (930 nm). The lowest excitation band peaks at 1.44 eV (860 nm) and the overlap between the emission and excitation bands is small. The X-ray excited luminosities range from 7 to 43 photons/keV. Thermally stimulated luminescence measurements show that n-type GaAs does not accumulate metastable radiative states that could cause afterglow. Further development and use with cryogenic photodetectors promises a remarkable combination of large target size, ultra-low backgrounds, and a sensitivity to electron recoils of a few eV that would be produced by DM particles as light as a few MeV/c2.