In this paper, the capacitance frequency dispersion in strong accumulation of capacitance voltage curves has been studied for different high-k dielectric layers in MOS stacks. By studying experimental data at low (77 K) and room temperature (300 K), in oxides with different density of defects, it was possible reflect the spatial distribution of the defects in the capacitance frequency dispersion. The experimental data show that while at room temperature, the capacitance dispersion is dominated by the exchange of carriers from the semiconductor into oxide traps far away from the interface, at low temperature the oxide traps near the Al2O3/InGaAs interface are responsible for the frequency dispersion. The results indicate that the capacitance dispersion in strong accumulation reflect the spatial distribution of traps within the oxide, and that dielectric/semiconductor conduction band offset is a critical parameter for determining the capacitance dispersion for Al2O3/InGaAs based gate stacks.