Silicon-based tandem solar cells have been emerged last years as promising design for low-cost high-efficiency solar cell. However, it is hard to find a matched-bandgap material with silicon (1.7 - 1.8eV). InGaN alloy is an interesting candidate due to its adjustable bandgap from 0.7eV (InN) to 3.44eV (GaN) and high absorption coefficient, so that a thin layer (less than 1µm) is sufficient to absorb incident light. However, such thicknesses for InGaN are difficult to grow due to the relaxation issue in material. It has been proved previously that the relaxation during growth process can be avoided by Semibulk structure. In this communication, we present a double-junction solar cell with a crystalline silicon solar cell as a bottom junction and an InGaN-based semibulk-structured solar cell as a top junction. We have modeled this structure using Silvaco-ATLAS TCAD software taking into account polarization effect in III-N materials. In spite of good morphology of semibulk structure, for high indium composition (50%), which is needed for current matching, the structure shows lower performance compared to ideal bulk-structured tandem cell. Thus, we have modeled a 4-terminals solar cell with relatively low indium composition (In=30%) where current matching is not needed. In both cases, results have shown an enhancement in total efficiency compared to Si single-junction solar cell.