Speaker
Description
N-type GaAs crystals doped with Silicon and Boron have recently attracted attention due to their high brightness at cryogenic temperatures, a property of particular relevance to light dark matter detection and other low-background experiments. However, this behavior appears inconsistent with the material’s high refractive index and narrow-beam absorption, which should strongly suppress photon extraction from the crystal bulk.
A possible explanation for the high light output observed in n-type GaAs at low temperatures is that much of the narrow-beam absorption is a previously unmeasured volumetric elastic scattering process that randomizes photon directions within the crystal.
We investigate this hypothesis by illuminating a 4 mm thick n-type GaAs crystal with an infrared laser at cryogenic temperatures and, to reduce systematic uncertainties, simultaneously and independently measure both its narrow beam transmission and bulk scattering intensity. To interpret the observations, we employ Monte Carlo simulations of photon transport that incorporate both elastic scattering and absolute absorption coefficients. Comparison between simulation and experimental data provides insight into this new internal scattering mechanism of n-type GaAs under cryogenic conditions.
