Electrical activity of deep levels in the presence of InAs/GaAs quantum dots

Deep level transient spectroscopy (DLTS) was used to measure the electrical activity of deep-level defects present in samples with InAs/GaAs quantum dots (QDs). Two of three electron traps revealed in DLTS spectra were identified as related to the EL2 family and the VGa-O center, respectively. The presence of oxygen in the structures was confirmed by secondary ion-mass spectrometry (SIMS) analysis. All traps exhibited extremely non-homogenous spatial distributions. It was concluded that intrinsic point defects at a significantly increased concentration were produced. They accumulated in front of QDs at distances, which are in the range of characteristic sizes of the wave-guides in semiconductor lasers. Consequently, the formation of oxygen-related traps may tend to occur in real device structures, which can be a serious limitation of laser performance if QDs are used as the active region and AlGaAs layers serve optical and electrical confinement.