Speaker
Description
Amorphous selenium (a-Se) offers direct detection of vacuum-ultraviolet (VUV) scintillation photons produced in cryogenic noble-element detectors. We present recent advances in the development of a-Se based VUV photodetectors at the University of Texas at Arlington. Our group has demonstrated direct response of a-Se photodetectors at 130 nm and low-light (~200 photons) performance at 401 nm and 165 K and has developed a model for field- and temperature-dependent charge transport and avalanche multiplication in lateral a-Se devices. We discuss our efforts to apply these lateral devices in QLUX, an experiment which integrates ionization-charge collection and a-Se scintillation-light detection within a common module. We will discuss further improvements to lateral devices including selective growth of electron- and hole-blocking layers on the interdigitated electrodes to suppress unwanted injection while preserving photogenerated-charge collection.
We then present progress in our parallel effort on vertical photodetector geometries, in which a-Se devices are coupled with VUV-transparent graphene top electrodes, including fabrication strategies, transparency measurements and visible-light photo response down to 77 K. We discuss the challenges of extending this architecture to stable avalanche operation through the implementation of VUV-transmitting hole-blocking contacts.
We briefly discuss other avenues we are exploring to improve detector performance, including field shaping for unipolar charge sensing and controlled avalanche multiplication, and superlattice structures for investigating interface-mediated control of charge transport and multiplication. Through these efforts, we aim to make a-Se a competitive photo detector technology for next-generation high-energy physics experiments, targeting efficient VUV detection with a few-photon sensitivity at cryogenic temperatures.