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.

Selective area laser-assisted doping of SiC thin films and blue light electroluminescence

“…The laser-assisted doping on an intrinsic SiC film in the phosphoric solution resulted in the n-type conductivity and the corresponding carrier concentration of ∼9.0 × 10 18 cm −3 , was approximately similar to the reported value elsewhere [36]. The carrier mobility of p-type 4H-SiC from the Halleffect measurement was found to be 152 cm 2 V −1 s −1 , which is in reasonable agreement with the literature value [20,35] of (100-161) cm 2 V −1 s −1 . Similarly, the carrier mobility of n-type 4H-SiC was measured to be 270 cm 2 V −1 s −1 , which was also in a reasonable agreement with the literature value [36] of ≈300 cm 2 V −1 s −1 .…”

“…This challenge can be overcome by using a localized nanosecond pulsed laser assisted doping in selective areas on SiC thin films deposited on a suitable substrate. Doping of SiC thin films without any surface defects can be obtained by Laser-assisted doping in gas-or liquid-or solid-phase [18][19][20][21][22][23][24]. In the laser-assisted liquid-phase doping method, the laser treatment is provided to diffuse the dopants into the SiC film which are immersed in suitable dopant precursor [25].…”

Formation of low resistance contacts to p-type 4H-SiC using laser doping with an Al thin-film dopant source

“…[9][10][11][12][13][14] Recently, we have shown that it is able to form a highly doped layer by laser irradiation to an Al thin-film deposited on the 4H-SiC surface as a diffusion source. 15) In this paper, we show that very low resistance contacts can be formed by using this doping method which does not require high-temperature annealing. The carbon face (C-face) of 4H-SiC is used in the investigation since this face composes the back side of usual MOS-gated devices.…”

High-Concentration, Low-Temperature, and Low-Cost Excimer Laser Doping for 4H-SiC Power Device Fabrication

“…In particular, it is more difficult to reduce a ptype resistance of SiC than an n-type resistance [1], while a p-type layer is essential to fabricate power devices with high-breakdown and low-loss such as PiN diodes, MOS-FETs, and IGBTs. We reported that high concentration (~10 21 cm −3 ) Al can be doped into SiC by KrF excimer laser ablation of an Al film deposited on the substrate [2,3]. There are other methods of laser doping of Al with wet-chemical dopants such as Al chloride solution [4 -6], but it is difficult to apply Al chloride solution as part of the fabrication process in terms of maintenance costs.…”