The well and barrier widths of MOVPE-grown In1-xGaxAs/InP (x = 0.47) quantum well (QW) structures have been examined by secondary ion mass spectroscopy (SIMS). The well widths varying from 25 to 150 Angstrom were also estimated through photoluminescence (PL) measurements. It was found that the differences in estimation of well width by PL and SIMS are due to differences in sputtering rates between InGaAs and InP during SIMS measurements, the rate being found to be 1.38-1.97 times less for the former. The presence of interfacial layers of similar to 2 monolayers width between well and barrier with low sputtering rate was also inferred.