I. P. Kazakov

Dynamic characteristics of “low-temperature” gallium arsenide for terahertz-range generators and detectors

The lifetime of free photoexcited carriers in epitaxial films of “low-temperature” gallium arsenide (LT-GaAs) is determined by the pump-probe optical reflection method. The dark resistivity of LT-GaAs layers is estimated. Emission spectra of LT-GaAs photoconductive antennas are measured in the terahertz frequency region by the Fourier transform spectroscopy.

Comprehensive study of structural and optical properties of LT-GaAs epitaxial structures

The results of the comprehensive study of LT-GaAs epitaxial structures on GaAs and Si substrates by high-energy electron diffraction, reflection anisotropy spectroscopy, atomic force microscopy, X-ray diffraction, Raman scattering, and photoluminescence methods are presented. The results obtained indicate the existence of several channels of nonequilibrium carrier recombination, which depend, in particular, on the substrate type and on the complex dependence of the concentration of structural imperfections on the used technology and growth conditions of the structures.

GaAs/Ge/GaAs Heterostructures for Use in Nonlinear Optics

GaAs/Ge/GaAs heterostructures with sublattice reversed GaAs on Ge epilayers grown via molecular beam epitaxy (MBE) for periodic domain inverted structures are presented. For the first time, such structures are grown in separate MBE machines for GaAs and Ge with atmospheric wafer transfer. The high quality of the heterostructures is confirmed via X-ray diffraction and photoluminescence. It is proposed that the surfactants (Bi, Sb) be used to control the nucleation of GaAs epilayers on a Ge epilayer.

Resonant tunneling GaAs/AlGaAs quantum well structures for p-i-n photovoltaic cells

This study is devoted to the development of resonant-tunneling structures of quantum wells implementing resonant matching of lower subbands of size quantization in an electric field of the p-i-n junction of photovoltaic elements. The method for controlling the lower subband position in quantum wells by introducing a series of the tunnel-transparent barriers into a quantum well is proposed. The possibility of varying the level position in deep quantum wells in a wide range up to the continuous spectrum is demonstrated on a grown model structure; in this case, agreement between calculated and experimental subband positions is achieved.

Orientation-patterned templates GaAs/Ge/GaAs for nonlinear optical devices. I. Molecular beam epitaxy

GaAs/Ge/GaAs heterostructures in which the GaAs layer lattice on Ge is rotated at a right angle to the substrate plane are grown by molecular-beam epitaxy (MBE). Such heterostructures are grown in different epitaxial setups for GaAs and for Ge with wafer transfer through air tor the first time. It is proposed to use surfactants (Bi, Sb) to control GaAs layer nucleation on Ge.

Orientation-patterned templates GaAs/Ge/GaAs for nonlinear optical devices. II. Investigation of properties

GaAs/Ge/GaAs heterostructures in which GaAs layer lattices are rotated at a right angle in the substrate plane are studied. High quality of heterostructures is confirmed by X-ray diffraction and photoluminescence methods.

Diagnostics of heterostructures of resonant-tunneling diodes during epitaxial growth. II. Monitoring techniques based on reflection method

It is shown that the reflection methods, in particular, the reflection anisotropy method, can be efficiently used for in situ studying and monitoring the growth of heterostructures with layers thinner than 10 monolayers. A change in the layer composition at direct GaAs/AlAs heterointerfaces of the active region of the resonant-tunneling diode is recorded by the reflection anisotropy method with a thickness resolution of ∼1 monolayer immediately during the growth. To estimate the quality of the formed active region of the resonant-tunneling diode, comparative reflection anisotropy spectroscopy is used.

Single-well resonant-tunneling diode heterostructures based on In0.53Ga0.47As/AlAs/InP with the peak-to-valley current ratio of 22:1 at room temperature

Current-voltage (I–V) characteristics of resonant-tunneling diode In0.53Ga0.47As/AlAs/InP structures are studied at 300 and 77 K. The peak-to-valley current ratios were determined as 22:1 and 44:1 at temperatures of 300 and 77 K, respectively, which correspond to the maximum values for InGaAs/AlAs/InP heterostructures without an additional InAs layer of a quantum subwell in their configuration.

Diagnostics of heterostructures of resonant-tunneling diodes during epitaxial growth. I. Estimation of the required accuracy of heterostructure growth

Based on the solution to the one-electron Schrödinger equation, current-voltage characteristics of the resonant-tunneling diode based on GaAs/AlAs are numerically simulated. It is shown that the layer thickness accuracy during epitaxial growth of the diode active region should be no worse than one monolayer.

Photoluminescence characterization technique for resonant-tunneling structures based on a long-period GaAs/AlGaAs superlattice, applicable at different stages of fabrication

A technique is developed for the photoluminescence-spectroscopy characterization of resonant-tunneling structures based on a long-period GaAs/AlGaAs superlattice that can be used for quality evaluation at all the stages of fabrication, including molecular-beam epitaxy, photolithography, and annealing. Factors such as the small energy difference between the quantum confined states in wide quantum wells, which make the photoluminescence characterization of such structures more difficult are taken into account. The long-period multiquantum-well structures are promising for the development of a new kind of solid-state intersub-band-transition devices emitting the narrow band radiation in far infrared. Their potential is essentially based on the fact that the scattering and the decay of carriers in the lower quantum-confined states may or may not involve optical phonons. The technique works at both liquid-helium and room temperature. It helps one optimize the process conditions to fabricate high-quality wide-quantum-well structures with excellent uniformity and desired parameters.