The temperature dependence of the spatial resolution of capacitance-voltage(C−V)profiles in the compositional quantum well (CQW) is investigated. The apparent carrier distribution (ACD) peak in theIn0.2Ga0.8As/GaAssingle QW is observed to show a strong temperature dependence, compared to that in Si &dgr;-doped GaAs. The ACD peak in CQW is wider (narrower) than the spatial extent of ground-state wave function at high (low) temperatures. The self-consistent numerical simulations on the carrier distribution show that the full width at half maximum of ACD peak in CQW is mainly affected by the debye averaging process at high temperatures and the change in the position expectation value of the two-dimensional electrons at low temperatures. This change in the position expectation value is found to be much smaller than the spatial extent of ground-state electron wave function. ©1998 American Institute of Physics.