Reduction of traps and improvement of carrier lifetime in 4H-SiC epilayers by ion implantation

The carrier traps Z1/2 and EH6/7 can be created by displacement of carbon atoms caused by electron radiation. After implanting carbon atoms(concentration:1.5e17cm-3) into the shallow surface of 4H-SiC epilayer and annealing, DLTS and TRPL was used for characterization. The carrier lifetime increased from 122 to 218ns and the trap concentration decreased from 3e13 to below 5e11cm-3. The reverse correlation between carrier lifetime and trap concentration agrees well in annealing temperature of 800°C-1800°C. Samples implanted with silicon atoms showed similar results after 1600°C annealing.

It can be inferred that carbon interstitials in the implanted layer can indiffuse during annealing and recombine with carbon vacancies in the epilayer, so that point defects disappear. Thus the Z1/2 and EH6/7 traps relate to the carbon vacancies, which was supported by later research.

Further reading:L.Storasta and H.Tsuchida, “Reduction of traps and improvement of carrier lifetime in 4H-SiC epilayers by ion implantation” ，Appl.Phys.Lett.90,062116(2007)