COMPARISON OF ALUMINUM-IMPLANTED AND BORON-IMPLANTED VERTICAL 6H-SIC P+N JUNCTION DIODES

The electrical performance of mesa type 6H-SiC p(+)n junction diodes f ormed via high temperature implantation of Al-27 and B-11 has been com paratively studied and analyzed at temperatures up to 400 degrees C us ing the Shockley model and the space-charge-limited current model. The Al-implanted diodes show better forward current-voltage characteristi cs with the best ideality factor obtained at 400 degrees C of 1.6 whil e that for B-implanted diodes is 1.3. The factor that prohibits the fo rward performance of the Al-implanted diodes appears to be the deep de fect center located at 1.2 eV above the valence band while that of B-i mplanted diodes appears to be the deep boron center called D-center lo cated at 0.7 similar to 0.8 eV above the valence band. On the other ha nd, B-implanted diodes show a better yield in the reverse direction wi th at least an order-of-magnitude lower reverse leakage current than t hat of Al-implanted diodes at all measurement temperatures. Several mi cropipe microplasmas were plainly visible in the middle of the mesa of the Al-implanted diodes when biased at -250 V but not on boron device s. The forward voltage drop of Al-implanted diodes is tightly distribu ted at 2.2 V with a forward resistance of 125 Omega while that of B-im planted diodes is broadly distributed with an average value of 2.8 V a nd nearly 200 times larger forward resistance. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.