InAsxP1-x/InP "surface" single quantum wells were formed at 600 degrees C by exposing InP surfaces to an AsH3 ambient and subsequently capping it with InP layers by metalorganic chemical vapor deposition (MOCVD). The effect of PH3/H-2 purge after the AsH3 exposure on the As amount and its distribution in the quantum wells was quantitatively analyzed by a combined method using grazing incidence X-ray reflectivity and photoluminescence (GIXR/PL). It was found that the As amount in the well decreased linearly with PH3 purge time, however, 2.5 monolayers of As remained in the well even after an extended purge time of 10 s. PH3 purge was approximately 10 times more efficient than H-2 purge in reducing the As amount. Irrespective of the different As amounts at various purging conditions, the characteristic As carryover length remained fairly constant at 1.7 nm, strongly suggesting that the As carryover mechanism was unaffected by the variation in purging conditions.