The current–voltage (I–V) and capacitance–voltage (C–V) behaviors of the (Au/Ni)/HfAlO3/n-Si (MIS) junctions at room temperature under white light with various intensities were investigated. The ln(I)–V curves show two linear behavior regions at about 1 V before and after the point of intersection that can be defined as two separate current-conduction (CMs) Mechanisms. The values of the ideality factor (n) and the zero-bias barrier height (ΦB0) were extracted using the slope and intercept of the ln(I)–V curve before and after the intersection point based on lighting power. Although the ΦB0 values decrease with increasing light power, n increases for two regions, and there is a strong linear relationship between them. The values of photo-current (Iph) increase with the increasing lighting power due to the formation of electron–hole pairs. The slope of the double-logarithmic Iph–P was changed from 0.422 to 0.852, respectively, at − 2 V and − 9 V, which indicates the ongoing distribution of Nss. In addition, the profile of surface states (Nss) ionized by light was obtained from the capacitance measured in dark and under lighting at 1 MHz. The Nss–V curve has two characteristic peaks that correspond to the region of depletion and accumulation due to a special distribution of Nss and their restructuring and reordering under the effects of lighting and an electric field.