The two independent As carryover processes were observed by photoluminescence (PL) and high-resolution X-ray diffraction (HRXRD) from the same InAsxP1-x/InP single quantum well(SQW) samples formed after AsH3 exposure. The combination of the SQW with a very thin InP capping layer enabled us to observe by HRXRD the weak modulation peaks from the InP buffer layer, where a minute amount of As was incorporated due to the As carryover from the interior of the reactor. Simultaneously the PL peak energies blue-shifted with AsH3 treatment temperature due to the excess As adsorbed on the InP surface. These results clearly show that the As carryover from two sources occurs independently, and simultaneously.