Defects in the GaAs and InGaAs layers grown by low-temperature molecular-beam epitaxy

The problem of defect formation in the GaAs and InGaAs layers grown by low-temperature molecular-beam epitaxy is discussed. The effect of growth conditions (temperature and flux ratio between the elements of groups III and V) on the morphology of growth surface, internal structure, type, and concentration of electrically-and optically active defects is analyzed. A comparison is made between the defect formation processes occuring during the epitaxial growth and post-growth annealing of the layers. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 63–72, December, 2006.     

Structure and properties of epitaxial GaAs and InGaAs films grown by low-temperature molecular-beam epitaxy

We study epitaxial GaAs and InGaAs films produced by molecular-beam epitaxy in the temperature range 150–480°C and with various arsenic partial pressures. We determine the structural and electrophysical characteristics of the film (the excess arsenic, the crystal lattice parameter, and the carrier concentration and mobility) as a function of the growth conditions. The influence of annealing on the cluster-structure formation in low-temperature MBE films, and on their properties, is also studied. In low-temperature GaAs we find a characteristic microwave absorption signal indicating the presence of a superconducting phase. We discuss the possible nature of this phase with regard to clusters of gallium or an In-Ga alloy. Siberian V. D. Kuznetsova Physicotechnical Institute, Tomsk State University. Tomsk State University. Semiconductor Physics Institute, Siberian Division, Russian Academy of Sciences. A. F. Ioffe Physicotechnical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika No. 9, pp. 37–45, September, 1998.     

An STM study of molecular-beam epitaxy growth of GaAs

Scanning tunneling microscopy has been used to investigate molecular-beam epitaxy growth of GaAs. By quenching the sample during deposition, we have imaged the GaAs(001) surface as it appeared during growth. Large scale images of the surface have been obtained at coverages varying from 0.25 to 1500 layers.     

High-temperature photoluminescence of CdHgTe solid solutions grown by molecular-beam epitaxy

The spectra of the high-temperature (up to 300 K) photoluminescence of the heteroepitaxial structures based on the CdHgTe solid solutions that are grown using molecular-beam epitaxy and emit at room temperature in the wavelength interval λ = 1.5–4.3 μm are analyzed. It is demonstrated that the observed photoluminescence of the CdHgTe narrow-gap semiconductor at high temperatures and the specific features of the high-temperature spectra can be interpreted using the disorder of the solid solution as in the case of the solid solutions of the group-III nitrides.     

Thermal stability of CdZnO thin films grown by molecular-beam epitaxy

CdZnO thin films with near-band-edge (NBE) photoluminescence (PL) emission from 2.39 eV to 2.74 eV were grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates with 800 °C in situ annealing. CdZnO thin films evolve from pure wurtzite (wz) structure, to mixture of wz and rock-salt (rs) structures confirmed by X-ray diffraction studies. Rapid-thermo-annealing (RTA) was performed on in situ annealed CdZnO samples. Pure wz CdZnO shows insignificant NBE PL peak shift after RTA, while mixture structure CdZnO shows evident blue shifts due to phase change after annealing, indicating the rs phase CdZnO changes to wz phase CdZnO during RTA process.     

Optical investigations of GaAs/Ga1−x Al x As Quantum wells grown by molecular-beam epitaxy

Summary Measurements of photoluminescence, excitation photoluminescence and reflectance are performed at various temperatures on a series of GaAs/Ga_1−x Al _x As quantum well structures grown by molecularbeam epitaxy. The selective photoluminescence data of the GaAs buffer layers are analysed in order to correlate the optical properties with the growth conditions. The Stokes shift of the excitation emission line from quantum wells is investigated under various excitation conditions. A considerable decrease of the Stokes shift is observed in the case of nonresonant and intense excitations. Also the extrinsic photoluminescence, as well as its temperature dependence, are interpreted. In addition, the temperature effects on both the bulk and quantum well spectra are shown to clarify the excitation features and the contribution of the interband transitions. To speed up publication, the authors of this paper has agreed to not receive the proofs for correction.     

Infrared lattice-reflection spectroscopy of Zn1−x CdxSe epitaxial layers grown on a GaAs substrate by molecular-beam epitaxy

Results are presented of the first measurements of infrared reflection spectra of Zn_1−x Cd_xSe films (x=0–0.55; 1) grown on a GaAs substrate by molecular-beam epitaxy. It is shown by a mathematical analysis of the experimental spectra that the investigated Zn_1−x Cd_xSe alloy system manifests a unimodal rearrangement of its vibrational spectrum as the composition is varied. Fiz. Tverd. Tela (St. Petersburg) 41, 982–985 (June 1999)     

Thickness uniformity of silicon layers grown from a sublimation source by molecular-beam epitaxy

The thickness distributions of epitaxial layers over the substrate area are experimentally and theoretically studied for deposition from a molecular beam formed by a sublimation source in vacuum. The calculated data agree well with the experimental results for the molecular-beam epitaxy of silicon.     

Electron diffraction on GaAs nanowhiskers grown on Si(100) and Si(111) substrates by molecular-beam epitaxy

The crystal structure of GaAs nanowhiskers grown by molecular-beam epitaxy on Si(111) and Si(100) substrates is investigated using reflection high-energy electron diffraction (RHEED). It is revealed that, in both cases, the electron diffraction images contain a combination (superposition) of systems of reflections characteristic of the hexagonal (wurtzite and/or 4H polytype) and cubic (sphalerite) phases of the GaAs compound. The growth on the Si(111) substrates leads to the formation of nanowhiskers with hexagonal (wurtzite and/or 4H polytype) and cubic (sphalerite) structures with one and two orientations, respectively. In the case of the Si(100) substrates, the grown array contains GaAs nanowhiskers that have a cubic structure with five different orientations and a hexagonal structure with eight orientations in the (110) planes of the substrate. The formation of the two-phase crystal structure in nanowhiskers is explained by the wurtzite—sphalerite phase transitions and/or twinning of crystallites.