Thermal annealing of defects in InGaAs/GaAs heterostructures with three-dimensional islands

A report is presented on the investigation of the influence of in situ anne aling of the InGaAs layer in p-n InGaAs/GaAs structures grown by the metall oorganic chemical vapor deposition upon the formation of coherently straine d three-dimensional islands. The structures were studied by the methods of capacitance-voltage measurements, deep-level transient spectroscopy, transm ission electron microscopy, and photoluminescence. It is established that t hree-dimensional islands with misfit dislocations are formed in the unannea led structure A, while quantum dots are formed in the annealed structure B. The deep-level defects were investigated. In structure A, defects of vario us types (EL2, EL3 (I3), I2, HL3, HS2, and H5) are present in the electron- accumulation layer. Concentrations of these traps are comparable to the sha llow donor concentration, and the number of hole traps is higher than that of the electron traps. On the in situ annealing, the EL2 and EL3 defects, w hich are related to the formation of dislocations, disappear, and concentra tions of the other defects decrease by an order of magnitude or more. For s tructure A, it is established that the population of the quantum states in the islands is controlled by the deep-level defects. In structure B, the ef fect of the Coulomb interaction of the charge carriers localized in the qua ntum dot with the ionized defects is observed. (C) 2000 MAIK "Nauka/Interpe riodica".