The effect of growth interruption (GI) on the quality of interface between InGaAs quantum well (QW) and InP layer has been studied using transmission electron microscopy (TEM). The In1-xGaxAs (x=0.39) QW grown without GI has sharp and coherent interfaces. However, cellular structure instead of InGaAs QW was observed in the sample grown with 120 sec AsH3 purge during the first GI (before the growth of InGaAs QW). According to the composition analysis using energy dispersive X-ray (EDX), inside of cell is InP and boundary of cell is considered to be a mixture of In1-xGaxAs1-yPy and InAs1-xPx phases. Similar structure was observed in the sample grown with 30 sec AsH3 purge after 30 sec PH3 purge during the first GI. Our results indicate that long time AsH3 purge during the first GI is detrimental to the formation of InGaAs QW. For the sample grown with AsH3 purge less than 40 sec during the second GI (after the growth of InGaAs QW), InGaAs QW is formed with sharp and coherent interfaces. However, if the surface of InGaAs QW is exposed to AsH3 gas for long time (~ 120 sec), dislocations are generated at the interface bewteen InGaAs QW and InP cap layer.