Search

High-voltage gradual p0–i–n0 junctions of AlxGa1 –xAs1 –ySby with x ~ 0.24 and y ~ 0.05 in the i‑region were studied using capacitance-voltage characteristics method and transient spectroscopy of deep levels. It has been established that the effective recombination trap in them is the DX-center of the Si donor impurity, with a thermal activation energy Et = 414 meV, a capture cross section σn = 1.04 × 10–14 cm2, and a concentration Nd = 2.4 × 1015 cm–3. In the heterostructures studied, there were no deep levels associated with dislocations. [ABSTRACT FROM AUTHOR]

A study of deep levels in InGaAs/GaAs and GaAsSb/GaAs p0–i–n0 heterostructures with misfit dislocations and identification of the effective defects responsible for the significant (by up to a factor of 100) decrease in the relaxation time of nonequilibrium carriers in the base layers (and in the related reverse recovery time) of InGaAs/GaAs and GaAsSb/GaAs high-voltage power p-i-n diodes is reported. Experimental capacitance–voltage characteristics and deep-level transient spectroscopy spectra of p+–p0–i–n0–n+ homostructures based on undoped GaAs layers without misfit dislocations and InGaAs/GaAs and GaAsSb/GaAs heterostructures with a homogeneous network of misfit dislocations, all grown by liquid-phase epitaxy, are analyzed. Acceptor defects with deep levels HL2 and HL5 are identified in GaAs epitaxial p0 and n0 layers. Dislocation-related electron and hole deep traps designated as ED1 and HD3 are detected in InGaAs/GaAs and GaAsSb/GaAs heterostructures. The effective recombination centers in the heterostructure layers, to which we attribute the substantial decrease in the relaxation time of nonequilibrium carriers in the base layers of p-i-n diodes, are dislocation-related hole traps that are similar to HD3 and have the following parameters: thermal activation energy Et = 845 meV, carrier capture cross-section σp = 1.33 × 10−12 cm2, concentration Nt = 3.80 × 1014 cm−3 for InGaAs/GaAs and Et = 848 meV, σp = 2.73 × 10−12 cm2, and Nt = 2.40 × 1014 cm−3 for the GaAsSb/GaAs heterostructure. The relaxation time of the concentration of nonequilibrium carriers in the presence of dislocation-related deep acceptor traps similar to HD3 was estimated to be 1.1 × 10−10 and 8.5 × 10−11 s for, respectively, the InGaAs/GaAs and GaAsSb/GaAs heterostructures and 8.9 × 10−7 s for the GaAs homostructure. These data correspond to the relaxation times of nonequilibrium carriers in the base layers of GaAs, InGaAs/GaAs, and GaAsSb/GaAs high-voltage power p-i-n diodes. [ABSTRACT FROM AUTHOR]

The temperature dependences of the capacitance–voltage characteristics and deep-level spectra of a Au–n-Si:Au–Si–p-Si heterostructure based on a composite layer of Au and Si nanoparticles are investigated. The structure manifests the properties of a transistor connected to a circuit with a common emitter with a disconnected base and an emitter Schottky barrier between the Au point contact and the n–(Si:Au) layer. Nanoparticles in this layer form finite clusters with hopping conductivity; herewith, charge accumulation is observed in the region of the Au point contact. The system at a measurement temperature below 180 K transitions from the finite-cluster phase to the infinite-cluster phase due to the percolation effect. This phase manifests metallic properties in the lateral plane of the heterostructure, which transforms into a p–n diode. [ABSTRACT FROM AUTHOR]

C-V characteristics and DLTS spectra of heterostructures made up of layers of closely packed amorphous Si nanoparticles deposited by laser electrodispersion onto single-crystal p-Si substrates have been examined. The patterns observed in the behavior of the C-V characteristics and DLTS spectra measured in the dark and under illumination with white light at various bias pulse voltages Ub and filling pulse voltages Uf suggest that the spatially localized amorphous Si nanoparticles have an average size of less than 2 nm, which is comparable with the de Broglie electron wavelength, and are characterized by quantum confinement. The ground and excited states of quantum dots are formed and exhibit the Stark effect and effects of electricdipole and controllable metastable occupancy under illumination. [ABSTRACT FROM AUTHOR]

Deep level transient spectroscopy (DLTS) measurements were performed to study electron emission from quantum states in a 20-layer Ge quantum-dot superlattice (QDSL) in a Ge/Si p-n heterostructure. It was established that the changes in the DLTS spectra depend heavily on the magnitude of the applied reverse bias U r . Three regions of the reverse bias U r were identified, corresponding to the manifestation of the three modes of the Wannier-Stark effect: Wannier-Stark ladder mode, Wannier-Stark localization, and nonresonant Zener tunneling mode. Furthermore, it was found that the appearance of DLTS peaks for all three modes is associated with electron emission from deep-level defects via Wannier-Stark localized states arising as a result of the splitting of the electron miniband of the Ge/Si QDSL. [ABSTRACT FROM AUTHOR]

The results of studies of hole energy states in vertically coupled quantum dots in InAs-GaAs p-n heterostructures by deep-level transient spectroscopy are reported. Spectra were recorded at different reverse-bias voltages. Levels related to bonding and antibonding s and p states of vertically coupled quantum dots were revealed. The energies of these states significantly depend on an external electric field applied to a heterostructure. This dependence was attributed to the quantum-dimensional Stark effect for the hole states of vertically coupled quantum dots. In addition to this, it was found that the energy of thermal activation of carriers from vertically coupled quantum dots depends on the conditions of isochronous annealing that was carried out both with the reverse bias switched-on and switched-off and both in the presence and absence of illumination. These changes, as in the case of isolated quantum dots, are typical of a bistable electrostatic dipole formed by carriers, localized in a coupled quantum dot, and ionized lattice point defects. The built-in electric field of this dipole reduces the energy barrier for the carriers in the coupled quantum dot. The investigated structures with vertically coupled quantum dots were grown using molecular-beam epitaxy taking account of self-assembling effects. [ABSTRACT FROM AUTHOR]

The Stark effect has been studied in multilayer InGaAs/GaAs laser structures with self-assembled quantum dots (QDs). A shift in the absorption edge depending on the reverse bias voltage has been measured in a two-section laser diode. The QD absorption edge shifts toward longer wavelengths with increasing electric field strength. It is established that the QD absorption depends on the polarization of light. The intensity at which TE-polarized luminescence in laser structures is studied is more than ten times higher than that of the TE-polarized emission component, which is explained by higher amplification of the TE mode. [ABSTRACT FROM AUTHOR]

Electron emission in a system of vertically coupled quantum dots (VCQDs) in InAs/GaAs p- n-heterostructures obtained by molecular beam epitaxy has been studied by means of deep-level transient spectroscopy (DLTS) as a function of the number of quantum dot (QD) rows and the reverse bias voltage. For a GaAs spacer thickness of d GaAs = 40 Å, the system occurs in a molecular state, irrespective of the number of QD rows. An increase in this number leads to a decrease in the Stark shift, which is probably related to a decrease in the lattice strain potential in the vicinity of VCQDs. [ABSTRACT FROM AUTHOR]