DescriptionThis thesis covers initiative works and innovative improvements in designing, fabricating and calibrating the world's first 4H-SiC single photon avalanche diodes (SPADs). In comparison to previous SiC APDs, the SiC SPADs have completely different targets. Major improvements are made in almost all aspects from wafer structure design, mask design, to characterizations. The robust and radiation-hard SiC SPADs, which are designed to replace the bulky PMTs and fragile Si SPADs, target at ultra high sensitive UV detection, towards the ultimate sensitivity--quantum limit. SiC SPADs can be widely used in missile and aircraft alarm system, none-line-of-sight (NLOS) and quantum communications, UV 3-D imaging, downhole exploration, as well as many NASA applications, such as low-earth orbit fluorescence observations.
The following areas are discussed in details in this thesis: wafer structure and mask design, a new bevel and MJTE edge termination technology for SiC SPADs, as well as improvements for an ultra low dark current, high quantum efficiency, and low dark count rate and high single photon detection efficiency. Future work is also proposed for further improving SiC SPADs.
The milestones in this thesis work include, the world's first SiC SPAD fabricated in 2004; the world's largest SiC SPAD (260µmx260µm) in 2004; a single photon counting measurement system with passive quenching circuit in 2004; a SiC SPAD with the highest gain (109) in 2005; a SiC SPAD with the lowest dark current ([less than]4fA at 50% of breakdown voltage and [less than]26fA at 95% of breakdown voltage) in 2007; the world's first SiC SAM SPAD with thick absorption layer, high quantum efficiency (~58%), and a significantly lower dark count rate than the first SiC SPAD in 2007; a new bevel edge termination technology; and a new p-type metal recipe leading to a low 10-4~ low 10-5Ωcm2 specific contact resistance for p-type 4H-SiC with minimum consumption of SiC ([less than]1500Å) in 2007.