We characterized the energy band of an In-rich InGaN/GaN quantum dot (QD) system with a metal-insulator-semiconductor (MIS) structure by performing optical and electrical measurements. We found several electron traps that have the activation energies of 0.16, 0.40, 0.61, and 0.73 eV with the emission cross sections of 2:16 Â 10 À19 , 2:23 Â 10 À16 , 8:61 Â 10 À15 and 3:04 Â 10 À16 cm 2 , respectively. The origins of the traps were considered to be an N-vacancy, a QD state, an anti-site point defect and an interface state of the MIS structure. The bound state of QDs was determined to be 0.40 eV from the edge of the GaN barrier and had a capture barrier of 0.16 eV generated by strain between the InGaN and GaN materials.