Wide bandgap Geiger mode photodiodes in AlGaAs

Emerging UV to blue light emitting scintillation materials promise improved radiation detection capabilities such as dual neutron-gamma detection and higher energy resolution. The use of traditional photomultiplier tubes (PMTs), with their associated high-voltage electronics often represents form factor and power-limiting component. The unique capabilities of a solid-state photomultiplier (SSPM) provides an alternative to PMTs. Though silicon based SSPMs (SiPMs) have been gaining wide attention in recent years, a major limiting factor is the dark current, especially for detectors that require sufficiently large detection area on a single chip. To scale up the detector area without drastic increase in dark current, we are developing new photodetector elements in Al
_0.8
Ga
_0.2
As. The wide-band-gap characteristic, combines with the maturity of GaAs material processing, makes Al
_0.8
Ga
_0.2
As an excellent material for developing large area SSPMs with lower dark current and high detection efficiency within the blue to UV region, which is important for state-of-the-art scintillation materials, such as LaBr3, CeBr3, and CLYC. This work presents the design, fabrication, and characterization results of Al
_0.8
Ga
_0.2
As Geiger mode photodiodes, as well as preliminary results of radiation hardness evaluation of these devices for harsh environment applications.