Abstract
The energy band structure and defect state of an InAs/InGaAs/GaAs quantum dot-infrared photodetector (QDIP) were characterized by performing capacitance–voltage and deep level transient spectroscopy measurements. We found a confined energy level of the InAs/InGaAs quantum dot in the InGaAs/GaAs quantum well. The confined energy in this QDIP structure was measured to be approximately 340 meV below the barrier edge which is located at the conduction band edge of the GaAs layer. This QDIP structure has also a point defect with an activation energy of 0.60 eV, which may be considered as an EL2 family in a GaAs material.