The capacitance-voltage characteristic of GaAs, In0.53Ga0.47As, and InAs metal-oxide-semiconductor capacitors (MOSCAPs) is calculated in three cases. First, quantization is not considered, then quantization of the C-valley is included, and finally quantization of the Gamma-, X-, and L-valleys is included. The choice of valley energy-minima is shown to determine the onset of occupation of the satellite valleys and corresponding increase in total capacitance. An equivalent-oxide-thickness correction is defined and used as a figure-of-merit to compare III-V to Si MOSCAPs and as a metric for the density-of-states bottleneck. (C) 2011 American Institute of Physics. [doi:10.1063/1.3652699]