Non-exponential capture of electrons in GaAs with embedded InAs quantum dots

InAs quantum dots grown in a GaAs matrix are investigated using capacitance transient spectroscopy and transmission electron microscopy (TEM). Trap st ates are measured which are associated with the presence of the quantum dot s but are too deep to be interpreted as the intrinsic electronic levels of the quantum dots. TEM allows us to rule out traps caused by threading dislo cations in the GaAs matrix. The trap occupation measured from capture data is a highly non-exponential function of the filling pulse duration and, tog ether with double DLTS measurements, indicate that the traps are electrical ly coupled in two dimensions and located in the plane of the dots. We propo se that the measured deep levels are due to point defects in or near the qu antum dots. (C) 1999 Elsevier Science B.V. All rights reserved.