A. E. Kunitsyn

Enhanced arsenic excess in low-temperature grown GaAs due to indium doping

We have found that isovalent indium doping enhances arsenic excess in GaAs films grown by molecular beam epitaxy at low temperature. An increase in lattice expansion and near infrared optical absorption, as well as higher density of As clusters, have been observed in the indium-doped films when compared to the conventional indium-free ones.

High-resolution x-ray diffraction study of InAs-GaAs superlattices grown by molecular-beam epitaxy at low temperature

InAs-GaAs superlattices grown by molecular-beam epitaxy at low temperature are investigated by high-resolution x-ray diffractometry. It is shown that despite a very high density of point defects due to the presence of excess arsenic, the as-grown superlattice has high crystal perfection. An analysis of the changes in the x-ray diffraction curves shows that high-temperature annealing, which is accompanied by the formation of As clusters and diffusion of indium, produces significant structural transformations in the GaAs matrix and at the interfaces.

Arsenic cluster superlattice in gallium arsenide grown by low-temperature molecular-beam epitaxy

Molecular-beam epitaxy at 200 °C is used to grow an InAs/GaAs superlattice containing 30 InAs delta-layers with a nominal thickness of 1 monolayer, separated by GaAs layers of thickness 30 nm. It is found that the excess arsenic concentration in such a superlattice is 0.9×1020 cm−3. Annealing the samples at 500 and 600 °C for 15 min leads to precipitation of the excess arsenic mainly into the InAs delta-layers. As a result, a superlattice of two-dimensional sheets of nanoscale arsenic clusters, which coincides with the superlattice of the InAs delta-layers in the GaAs matrix, is obtained.

Silicon and phosphorus co-implantation into undoped and indium-doped GaAs substrates

The electrical properties and low-temperature (4.2 K) photoluminescence of heavily doped n-type layers produced by silicon and silicon/phosphorus implantation into undoped and indiumdoped Czochralski grown semi-insulating GaAs substrates have been investigated. It is found that Si+P co-implantation results in suppression of deep levels in the anion sublattice, an increase of donor activation efficiency, and a sharper carrier concentration profile in both types of substrates. The use of indium-doped substrates enhances radiation defect annealing, but does not change the donor activation efficiency.

Doping of GaAs layers with Si under conditions of low-temperature molecular beam epitaxy

Using the methods of X-ray diffraction, optical absorption in the near-infrared range, and the Hall effect, the influence of growth conditions on the structure and properties of Si-doped GaAs layers grown by low-temperature molecular-beam epitaxy was investigated. The relation between the incorporation of excess As and electrical properties of the layers is analyzed.

Influence of indium doping on the formation of silicon-(gallium vacancy) complexes in gallium arsenide grown by molecular-beam epitaxy at low temperatures

Low-temperature photoluminescence (PL) studies of gallium-arsenide layers grown by molecular-beam epitaxy at low (200 °C) temperatures (LT GaAs) and doped with silicon or a combination of silicon and indium have been performed. The PL spectra of as-grown samples reveal a shallow acceptor-based line only. After annealing, an additional line at ∼1.2 eV appears, which is attributable to SiGa-VGa complexes. The activation energy of complex formation is found to be close to the activation energy of migration of gallium vacancies and is equal to 1.9±0.3 eV for LT GaAs: Si. It is found that doping with a combination of silicon and indium leads to an increase in the activation energy of formation of SiGa-VGa complexes to 2.5±0.3 eV. We believe that this increase in the activation energy is controlled by the gallium vacancy-indium interaction through local lattice deformations.

Effect of isovalent indium doping on excess arsenic in gallium arsenide grown by molecular-beam epitaxy at low temperatures

X-ray spectral microanalysis, optical transmission measurements at near-infrared wavelengths, and x-ray diffractometry are used to show that the isovalent indium doping of gallium arsenide during molecular-beam epitaxy at low temperatures leads to an increase in the concentration of excess arsenic trapped in the growing layer.

Properties of tellurium-doped gallium antimonide single crystals grown from nonstoichiometric melt

The electric and luminescence properties of tellurium-doped gallium antimonide single crystals grown from gallium-enriched melt by Czochralski’s method have been investigated. It was determined that the crystals possess n-type conductivity and are strongly compensated. It was found that toward the end of the ingot the concentration of the impurity tellurium increases more rapidly than that of the compensating acceptors. The possibilities of obtaining the properties of GaSb single crystals by growing the crystals from nonstoichiometric melts followed by heat treatment of the material are discussed.

LT GaAs delta-doped with In: enhanced As excess, In-Ga intermixing, As cluster array ordering

The effects of indium incorporation in GaAs grown by MBE at low substrate temperature (LT GaAs) have been studied. The 0.04% indium doping is shown to provide an increase in the As excess along with improved crystal quality. The In-Ga intermixing is found to enhance by almost two orders of magnitude due to a high point defect concentration in LT GaAs. The effective activation energy of the intermixing is determined from TEM measurements to be 1.1 eV. The As precipitation kinetics is found to be quicker in In-free regions than within the In-containing layers. Using these observations, we successfully formed a 30 nm period perfect superlattice consisting of thin (double cluster diameter) As cluster sheets separated by cluster-free LT GaAs spacers.

Control of point defects and arsenic clusters in low-temperature grown GaAs by isovalent impurity doping

We show that isovalent indium impurity doping can be employed to control excess-arsenic-related point defects and arsenic clusters in GaAs films grown by molecular-beam epitaxy at low temperature. In respect of arsenic excess, indium doping was found to be equivalent to a decrease in the growth temperature, but provided better crystalline quality of the material. Indium delta-doping was used to create two-dimensional sheets of arsenic clusters in the GaAs matrix. We demonstrate a 30-period superlattice of two-dimensional cluster sheets separated by cluster-flee spacers and two cluster sheets sandwiched between n- and p-GaAs layers grown at conventional temperature.