Al doping of 4H-SiC by laser irradiation to coated Al film and its application to junction barrier Schottky diode

Abstract

Aluminum (Al) is doped into 4H-SiC by excimer laser irradiation to a coated Al film on the 4H-SiC surface. Deep (∼200 nm in the depth) and high-concentration (over 1 × 1021/cm3 on the surface) Al doping is realized by adjusting the Al film thickness for the laser fluence. Optical emission measurements clearly show that Al plasma is generated on and above the sample surface by laser irradiation. Surface morphology observation suggests that, under an optimum combination between Al thickness and laser fluence, high-temperature molten Al is formed on the 4H-SiC surface and the molten Al serves as the dopant source. We adopt this laser Al doping to fabricate a junction barrier Schottky (JBS) diode. Selective doping is performed by using SiO2 as the doping mask. The fabrication is thoroughly carried out without heating the substrate except for film deposition and metal sintering processes. The fabricated JBS diode shows satisfactory operation as compared with a pn junction diode.