This paper presents the characterization of interface trap charge for 30 nm In0.53Ga0.47As channel Gate-all-around field effect transistor (GAAFET) using ALD Al2O3 as the oxide. The interface trap charge density (D-it) is extracted from CV model through self consistent iterations. The CV model is formulated by self consistent Schrodinger-Poisson solver. Wave function penetration effect has been considered while solving the Schrodinger equation. The result gives an intuition about the D-it profile. The difference between the initial assumed CV and the final CV demonstrates the effect of D-it on the CV profile of the device. We repeated the same for In.65Ga.35As and In.75Ga.25As and then did a comparative study of the devices. The donor-like traps dominate the D-it profile for higher mole-fraction of In in InGaAs which in our case is In0.75Ga0.25As. The stronger inversion of In-rich channels and hence, better transport characteristics is evident from these results.