In the present paper, we aim to report an ultra-compact AlGaAsκ(3) photonic crystal structure to realize multifunctional logic responses. The properties of the proposed model are numerically investigated with different physical parameters by the 2D-finite difference time domain (FDTD) method. For this purpose, the effect of the geometrical parameters and dielectric materials, including Si and InSb, in the near-infrared region are studied. To obtain dynamical tunability of the proposed model, the effect of the defects is then utilized. Numerical results show that the proposed devices are able to operate as multifunctional logic devices including an AND gate and a demultiplexer. Moreover, the structure has a compact footprint of 8.85 μm×8.85 μm×100 nm. We expect that this theoretical result leads to remarkable applications in photonic integrated circuits, e.g., optical memory.