Undoped and 0.1% 0.5% and 1.0% indium doped ZnO thin films were obtained by spin coating method as interfacial thin film layer between Al metal and p-Si semiconductor to investigate dielectric properties of the Al/In:ZnO/p-Si heterojunctions. Impedance spectroscopy technique was employed to characterize the dielectric properties of the Al/In:ZnO/p-Si heterojunctions depending on frequency (from 10 kHz to 1 MHz) and voltage (from −5 V to +5 V). The results imparted that interface states (Nss), series resistance (Rs), barrier height (Φb) and the concentration of acceptor atoms (Na) influenced frequency changes. The dielectric parameters such as dielectric constant (ε′), dielectric loss (ε″), loss tangent (tan δ), real and imaginary parts of the electric modulus (M′ and M″) and ac electrical conductivity (σ) values were calculated from impedance spectroscopy measurements and discussed in details for changing frequency and voltage for various In doped ZnO thin film interlayers. The dielectric properties of the Al/In:ZnO/p-Si heterojunctions were affected both In doping concentration and the frequency and voltage changes. The Al/In:ZnO/p-Si heterojunctions can be considered for industrial applications to increase the control.