GaAs as a Bright Cryogenic Scintillator for the Detection of Low-Energy Electron Recoils From MeV/c² Dark Matter

Snowmass2021 Cosmic Frontier: The landscape of low-threshold dark matter direct detection in the next decade

“…The phonon detectors will then be sensitive to the 1.33 eV scintillation photons produced by interactions in the crystal, while coincident detection of phonon signals enables discrimination of electronic recoil signals from nuclear recoil and heat-only backgrounds. GaAs also seems to have little to no afterglow [259,260].…”

How silicon and boron dopants govern the cryogenic scintillation properties of N-type GaAs

“…Figure 1. The GaAs energy gap and transition energies [2] (eV) for silicon donor electrons recombining with radiative acceptors A, B, C, and D, and with non-radiative acceptors X. Acceptors are shown empty as they would be after trapping a valence band hole.…”

“…The emission spectra of the four principal emission bands of GaAs(Si,B) have been previously reported. [2] Table III lists the filters (Edmund Optics Inc., Cupertino, CA), and Table IV lists the filter combinations used to measure the luminosities and decay curves of the four emission bands. The SP1200 filter was used to block band D emissions that are beyond the stopbands of the NB850, NB925, and NB1075 filters.…”

“…If necessary, antireflection coatings can be used to reduce internal trapping. [16] Note that the quantum efficiency of the R5509-43 phototube decreases above 1350 nm, which is near the peak of emission band D. Since band D extends to 1600 nm [2] a large fraction (possibly 50%) of the band D emissions are not included in LD or LU. Gamma ray spectroscopy would be a better way to measure luminosities, using a cryogenic germanium photodiode with a high quantum efficiency over the full GaAs emission spectrum.…”

“…In previous work, we determined that n-type GaAs doped with Si and B is a luminous cryogenic scintillator. [1,2] In this work, we explore the dependence of its scintillation properties on the concentrations of Si and B. The paper is organized as follows: Section 2 describes 29 GaAs samples, the pulsed X-ray system, the filters used, and the calibration and analysis procedures.…”