Ohmic contacts of 4H-SiC on ion-implantation layers

The ohmic contacts of 4H-SiC are fabricated on nitrogen ion implanted layers made by performing box-like-profile implantation three and four times. Implantation parameters such as the standard deviation σ and the projection range R p are calculated by the Monte Carlo simulator TRIM. Ni/Cr ohmic contacts on Si-face 4H-SiC implantation layers are measured by transfer length methods (TLMs). The results show that the values of sheet resistance R sh are 30 kΩ/□ and 4.9 kΩ/□ and the values of specific contact resistance ρ c of ohmic contacts are 7.1×10-4Ω·cm 2 and 9.5×10-5Ω·cm 2 for the implanted layers with implantation performed three and four times respectively.

Ohmic contacts of 4H-SiC on ion-implantation layers

Ion-implantation layers are fabricated by multiple nitrogen ion-implantations (3 times for sample A and 4 times for sample B) into a p-type 4H-SiC epitaxial layer. The implantation depth profiles are calculated by using the Monte Carlo simulator TRIM. The fabrication process and the $I$--$V$ and $C$--$V$ characteristics of the lateral Ti/4H-SiC Schottky barrier diodes (SBDs) fabricated on these multiple box-like ion-implantation layers are presented in detail. Measurements of the reverse $I$--$V$ characteristics demonstrate a low reverse current, which is good enough for many SiC-based devices such as SiC metal--semiconductor field-effect transistors (MESFETs), and SiC static induction transistors (SITs). The parameters of the diodes are extracted from the forward $I$--$V$ and $C$--$V$ characteristics. The values of ideality factor $n$ of SBDs for samples A and B are 3.0 and 3.5 respectively, and the values of series resistance $R_{\rm s} $ are 11.9 and 1.0~k$\Omega $ respectively. The values of barrier height $\phi _{\rm B} $ of Ti/4H-SiC are 0.95 and 0.72 eV obtained by the $I$--$V$ method and 1.14 and 0.93 eV obtained by the $C$--$V$ method for samples A and B respectively. The activation rates for the implanted nitrogen ions of samples A and B are 2{\%} and 4{\%} respectively extracted from $C$--$V$ testing results.