Two-Dimensional Analytical Model for Concentration Profiles of Aluminum Implanted Into 4H-SiC (0001)

A 2-D model of aluminum-ion implantation into 4H-SiC (0001) was developed and assessed through reverse current I_R-voltage V_R characteristics of p-n diodes. The model was based on a Monte Carlo simulation using a binary-collision approximation. For a moderate dose (10¹¹ - 10¹³ cm^-2), simulated isoconcentration contours were independent of the orientation of the masking edge. This condition allowed us to extract lateral straggling by expressing the lateral-concentration profiles as a 1-D dual-Pearson distribution function multiplied by a Gaussian distribution function. To demonstrate its applicability to higher doses, the model was applied in the simulation of a 4H-SiC p-n diode whose anode was formed by a 4 × 10¹⁴ cm^-2 aluminum implant into a moderately n-type doped (N_D = 9 × 10¹⁵ cm^-3) drift layer. The I_R-V_R characteristics calculated with the model were found to agree with the measured ones, suggesting that the developed model is appropriate for designing 4H-SiC power devices, including not only a p-type region with moderate aluminum implant but also a p-type region with a heavy aluminum implant on the condition that N_D is sufficiently high.