Search

In situ stress generation and relaxation in AlGaN/GaN/AlN heterostructure with an overall thickness exceeding 3 μm in the process of its growth on a 6 H-SiC substrate by low-temperature plasma-assisted molecular-beam epitaxy at substrate temperatures ranging from 690 to 740°C was studied. At room temperature, AlN and GaN layers revealed residual compressive stresses of-2.3 and-0.1 GPa, respectively. This made it possible to avoid cracking during postgrowth cooling of the structure. [ABSTRACT FROM AUTHOR]

We report on fabrication and studies of composite heterostuctures consisting of an Al0.55Ga0.45N/Al0.8Ga0.2N quantum well and surface Al nanoislands, grown by plasma-assisted molecularbeam epitaxy on c-sapphire substrates. The influence of a substrate temperature varied between 320 and 700ºC on the size and density of the deposited Al nanoislands is evaluated. The effect of Al nanoislands on decay kinetics of the quantum well middle-ultraviolet photoluminescence has been investigated by time resolved photoluminescence. The samples with the maximum density of Al nanoislands of 108 cm-2 and lateral dimensions in the range of 100-500 nm demonstrated shortening of the photoluminescence lifetime, induced by interaction of the emitting quantum well and the plasmonic metal particles. [ABSTRACT FROM AUTHOR]

Advances in the production technology of multiperiod nanoheterostructures of quantum-cascade lasers with 60 cascades by molecular-beam epitaxy (MBE) on an industrial multiple-substrate MBE machine are discussed. The results obtained in studying the nanoheterostructures of quantum-cascade lasers by transmission electron microscopy, high-resolution X-ray diffraction analysis, and photoluminescence mapping are presented. [ABSTRACT FROM AUTHOR]

InAs single hetero structure photodiodes were considered as alternatives to cooled CdHgTe-based detectors sensitive to radiation around 3 μm spectral region in a wide temperature range 77-300 K. Estimations of detectivity as well as p-n junction position in InAs heterostructures have been obtained via photoelectrical and AFM measurements. [ABSTRACT FROM AUTHOR]

The results of studies of the properties of composite InGaN/GaN/InAlN heterostructures are reported. It is shown that, in the InAlN layer, there is substantial phase separation that brings about the formation of three-dimensional islands consisting of AlN-InAlN-AlN regions. The dimensions of these islands depend on the thickness of the InAlN layer and the conditions of epitaxial growth. Interruptions in the growth of InAlN provide a means for influencing the structural properties of the InAlN islands. The use of composite InGaN/GaN/InAlN heterostructures, in which the InGaN layer with a high In content serves as the active region in light-emitting diode structures, makes it possible to achieve emission in the yellow-red wavelength range 560-620 nm. [ABSTRACT FROM AUTHOR]

The depth distribution of free carriers over the HEMT structures with quantum-well layers is studied by electrochemical capacitance-voltage profiling. It is shown that the actual distribution of the concentration of free carriers and their energy spectrum in the HEMT structure channel can be obtained by numerical simulation of the results of profiling based on the self-consistent solution of one-dimensional Schrödinger and Poisson equations. [ABSTRACT FROM AUTHOR]

Heterostructures with GaP/GaPN and GaP/GaPAsN quantum wells grown by the MOCVD method are studied by methods of capacitance-voltage profiling and capacitive and current deep level transient spectroscopy. In heterostructures with GaP/GaPN quantum wells, intrinsic defects with deep levels of 0.17 and 0.08 eV are revealed. It is shown that a considerable decrease in the concentration of these defects occurs with the substitution of a ternary GaPN alloy forming the region of the quantum well by a GaPAsN quaternary alloy. The nature of emerging defects and mechanisms of decreasing their concentration are discussed. [ABSTRACT FROM AUTHOR]

The influence of gamma radiation on multilayer AlGaAs/InGaAs/GaAs transistor heterostructures has been studied by means of X-ray diffraction analysis and transmission electron microscopy. It was found that irradiation with doses exceeding ∼3 × 107 rad leads to destruction of the GaAs layer on the surface of these structures. An irradiation dose of 108 rad significantly deteriorates the surface planarity, with the surface roughness reaching values of several nanometers. In addition, dislocations are formed in the cap layer of the structure. Such a behavior of the cap layer may be due to the existence of an oxide layer on its free surface and to the possible chemical reactions, induced by gamma radiation, between atoms of the cap layer and free radicals formed in the oxide and in the ambient atmosphere. No noticeable changes in the structure and composition of the thin InGaAs channel layer occur at doses lower than 108 rad. [ABSTRACT FROM AUTHOR]

The effect of doping level on the current–voltage characteristics of semiconductor heterostructures with GaAs/AlGaAs superlattices was studied by the electrochemical capacitance–voltage profiling method. It was shown that a high density of free electrons in the GaAs/AlGaAs superlattice screens the external electric field and inhibits the formation of a domain with a high electric field that is responsible for resonant tunneling in weakly coupled superlatticest. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]