Effects of Excimer Laser Irradiation on the Morphological, Structural, and Electrical Properties of Aluminum-Implanted Silicon Carbide (4H-SiC)

This paper reports on the effects of excimer laser irradiation on an aluminum (Al)-doped silicon carbide (4H-SiC) layer. Specifically, high-concentration (1 × 1020 at/cm3) Al-implanted 4H-SiC samples were exposed to a few pulses of 308 nm laser radiation (pulse duration of 160 ns), with fluence varying from 1.0 to 2.8 J/cm2. As a starting point, the laser-induced modifications of the morphological, microstructural, and nanoelectrical properties of the exposed 4H-SiC surface were monitored by combining different techniques. From these investigations, an evolution of the surface morphology was observed that can be ascribed to a conversion during irradiation of the uppermost part of the 4H-SiC implanted layer into a polycrystalline region of 3C-SiC and 6H-SiC grains, surmounted in the order by a crystalline-Si layer and an amorphous C-rich region. Then, the electrical characteristics of the implanted layer were evaluated by means of test structures appropriately fabricated on the samples. The high value of sheet-resistance of the irradiated layer (in the order of 104 kΩ/sq) suggested a poor activation of the p-type dopant and/or a low mobility of the carriers in the polycrystalline 3C-SiC/6H-SiC layer. The outcomes of this study can be useful for a fundamental understanding of laser annealing treatments of 4H-SiC implanted layers, toward a possible use in 4H-SiC technology of this process.