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The I-V characteristics of p+n 4H-SiC diode formed by Al ion implantation have been investigated as a function of annealing temperature. Al ions are implanted at the elevated sample temperature of 500 oC in order to fabricate p-type doped layer on the n-type epitaxial layer, grown on n+ 4H-SiC substrate. The implanted sample is annealed using electron bombardment annealing system in the annealing temperature ranging from 1700 to 1900 oC. The Al implanted sample, annealed below 1800 oC shows the deteriorated I-V characteristics in which the forward current includes the resistive current components and the reverse current is in the order of 10-4 A/cm2. The p+n diode formed by annealing at 1900 oC reveals the forward current without extra-current components and the reverse current as low as 10-6 A/cm2. It is suggested that the annealing above 1900 oC is effective in reducing the implantation-induced defect at the interface between Al implanted p+ layer and the underlying n-type epitaxial layer.

We fabricate pn-junction diode on p-type 4H-SiC(0001), in which n-type region is formed by N ion implantation at room temperature (total dose: 2.4 x 1015 /cm2, thickness: 300 nm) and subsequently annealed for 5 min using electron bombardment annealing system (EBAS). The root-mean-square (RMS) surface roughness and sheet resistance (Rs) for N ion implanted region, annealed at 1900 oC is estimated to be 0.7 nm and 940 4/sq., respectively. The alloyed Ni ohmic contact to N ion implanted layer, annealed at 1900 oC, shows the contact resistance (Rc) of 8.3 x 10-5 4cm2. The forward drop voltage at 100 A/cm2 and on-resistance of mesa-type pn junction diode is estimated to be 3.1 V and 1.3x10-2 4cm2. The reverse bias leakage current of that is 2.2 x 10-5 A/cm2 at 100 V. It is demonstrated that EBAS is able to apply for the fabrication of pn-junction diode.

In this paper, we demonstrate that high temperature and short time EBAS annealing is effective to obtain low sheet resistance without surface roughening in heavily Al-implanted 4H-SiC (0001) samples (Al concentration: 1.0 × 1021 /cm3, thickness: 0.3 microns, total dose: 2.6 × 1016 /cm2). The sheet resistance and rms surface roughness of the sample annealed at 1800 °C for 0.5 min is estimated to be 4.8k ohm/sq. and 0.82 nm, respectively. Also, we discuss the advantage of EBAS annealing for the suppression of surface roughening during annealing.