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The absorption of uncoupled and tunnel-coupled vertically correlated quantum dots (QDs), measured at room temperature, has been experimentally compared. It is revealed that matching of the laser wavelength and Stark shift for laser structures with tunnel-coupled QDs leads to resonant absorption with formation of bound and antibound exciton states with a splitting energy of ∼62 meV between them in QD molecules. For these states, an external field causes a large linear Stark shift (up to 68 meV). For uncoupled QDs, one resonant absorption peak with the formation of an exciton (for which the Stark shift does not exceed 13 meV) is observed. [ABSTRACT FROM AUTHOR]

Deep level transient spectroscopy (DLTS) is used to study electron emission from the states in the system of vertically correlated InAs quantum dots in the p-n InAs/GaAs heterostructures, in relation to the thickness of the GaAs spacer between the two layers of InAs quantum dots and to the reverse-bias voltage. It is established that, with the 100 Å GaAs spacer, the InAs/GaAs heterostructure manifests itself as a system of uncoupled quantum dots. The DLTS spectra of such structures exhibit two peaks that are defined by the ground state and the excited state of an individual quantum dot, with energy levels slightly shifted (by 1–2 eV), due to the Stark effect. For the InAs/GaAs heterostructure with two layers of InAs quantum dots separated by the 40 Å GaAs spacer, it is found that the quantum dots are in the molecule-type phase. Hybridization of the electron states of two closely located quantum dots results in the splitting of the levels into bonding and antibonding levels corresponding to the electron ground states and excited states of the 1 s +, 1 s −, 2 p +, 2 p −, and 3 d + types. These states manifest themselves as five peaks in the DLTS spectra. For these quantum states, a large Stark shift of energy levels (10–40 meV) and crossing of the dependences of the energy on the electric field are observed. The structures with vertically correlated quantum dots are grown by molecular beam epitaxy, with self-assembling effects. [ABSTRACT FROM AUTHOR]

Deep-level transient spectroscopy is used to study charge-carrier emission from the states of separate quantum dots in InAs/GaAs p–n heterostructures grown on (100)- and (311)A-oriented GaAs substrates in relation to the reverse-bias voltage U. It is established that the structures under consideration exhibit different bias-voltage dependences of the Stark shift for the energy levels of the quantum-dot states on the value of U. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Deep-level transient spectroscopy is used to study the emission of holes from the states of a vertically coupled system of InAs quantum dots in p-n InAs/GaAs heterostructures. This emission was considered in relation to the thickness of a GaAs interlayer between two layers of InAs quantum dots and to the reverse-bias voltage Ur. It is established that hole localization at one of the quantum dots is observed for a quantum-dot molecule composed of two vertically coupled self-organized quantum dots in an InAS/GaAs heterostructure that has a 20-A-thick or 40-A-thick GaAs interlayer between two layers of InAs quantum dots. For a thickness of the GaAs interlayer equal to 100 A, it is found that the two layers of quantum dots are incompletely coupled, which results in a redistribution of the hole localization between the upper and lower quantum dots as the voltage Ur applied to the structure is varied. The studied structures with vertically coupled quantum dots were grown by molecular-beam epitaxy using self-organization effects. [ABSTRACT FROM AUTHOR]

Microstructures in p–CuInSe[sub 2] single crystals tailored by the strong electric field have been studied using the method of local (d≲1 μm) cathodoluminescence (CL). The shortest-wavelength radiation (hω=1.023 eV) has been observed from the n-type layer and longer-wavelength radiation (hω=1.006 eV)—from the p-type regions. An analysis of the cathodoluminescence spectra has allowed us to attribute the experimental features to optical transitions associated with donor and acceptor levels of V[sub Cu],V[sub Se], and Cu[sub i] point defects in the crystal. Test measurements of EBIC, the C–V characteristics, and the DLT spectra confirm the cathodoluminescence data and reveal additional features of the p–n–p microstructures. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]