Defect states in InAs quantum dots characterized by photo-induced current transient spectroscopy

InAs quantum dots(QDs) were grown on semi-insulator GaAs substrate by Molecular Beam Epitaxy (MBE) and deep level defects related with InAs QDs were investigated with photoinduced current transient spectroscopy(PICTS). Six deep level defects are observed in the ranges from 127 meV to 532 meV in activation energy. Two defects, located at 127 and 156 meV, of them are dominant in intensity and are considered as the defects related with QDs. To identify their origins, the trapping kinetics of defects with the optical filling pulse was investigated and thermal annealing experiment were performed. From these results, it is suggested that the 127 meV-defect might be the isolated defect state introduced during the growth and the 156 meV-defect could be regarded as an extended defect, which is caused by strain effects between InAs and GaAs near QDs.