Simulation and characterization of an ultraviolet enhanced backside-illuminated Single-Photon Avalanche Diode

In this master thesis is simulated and characterized a novel SOI backside-illuminated SPAD designed especially to target the UV region in terms of photodetective capabilities. Backside-illumination has the pottential to increase the fill factor in SPAD arrays as the micro-cells and front-end electronics can be optimizedcseparately. The use of SOI technology allows the SPAD to limits absorption losses and improve photodetection efficiency thanks to the thin transparent BOX layer. The thin body and depletion region is optimizedcto absorb UV photon, which has great potential in applications where this wavelength range is in use such as positron emission tomography. The device is simulated with Silvaco’s process simulator (Athena) and device simulator (Atlas) that are used to model the doping profile, breakdown voltage, triggering probability and quantum efficiencies. The result for the breakdown voltage (8.3 V) is similar to earlier measurement made before this work. The simulated peak quantum efficiency in the case of backside-illumination is 67% at 450 nm which is a sensible value considering other state of the art devices, however it is quite far from the measured value which is more than 90%. Dark counts and afterpulse characterizations were attempted on another device using a Gaussian-shaping amplifier and post-processing methods for the signal analysis. The setup and methods are well suited for DCR characterization (136 cps/µm2 ) was measured at room temperature for an excess bias of 0.8 V and 94 cps/µm2 for sub-zero temperatures. However the amplifier output pulse did not allow to resolve afterpulses despite pulse pile-up correction and the pulse height histograms resulted in exponential decays which is unexpected and should be investigated.