V. V. Mamutin

Experimental and theoretical studies of phonons in hexagonal InN

The first- and second-order Raman scattering and IR reflection have been studied for hexagonal InN layers grown on (0001) and (1102) sapphire substrates. All six Raman-active optical phonons were observed and assigned: E2(low) at 87 cm−1, E2(high) at 488 cm−1, A1(TO) at 447 cm−1, E1(TO) at 476 cm−1, A1(LO) at 586 cm−1, and E1(LO) at 593 cm−1. The ratio between the InN static dielectric constants for the ordinary and extraordinary directions was found to be e⊥0/e∥0=0.91. The phonon dispersion curves, phonon density-of-state function, and lattice specific heat were calculated. The Debye temperature at 0 K for hexagonal InN was estimated to be 370 K.

Mg‐Doped Hexagonal InN/Al2O3 Films Grown by MBE

We report on the first attempts of Mg doping of hexagonal InN/Al2O3(0001) films grown by plasma-assisted molecular beam epitaxy. A dramatic improvement of crystalline quality of InN : Mg epilayers has been observed at the magnesium concentration in the 1019 to 3 ×1020 cm—3 range as indicated by triple-crystal X-ray diffraction θ-rocking curve peak width below 30 arcsec. An increase of Mg doping higher than 1021 cm—3 deteriorates dramatically the InN crystal quality and surface morphology. A thermodynamic model of the surfactant Mg effect is proposed. The increase in Mg concentration causes the reduction by an order of magnitude (down to n = 1019 cm—3) of free electron concentration in InN : Mg layers compared to undoped ones, accompanied by a significant reduction of electron mobility. This behavior can be explained by a complex effect of the crystal quality improvement and the carrier compensation by incorporated Mg acceptors.

Transmission Electron Microscopy of GaN Columnar Nanostructures Grown by Molecular Beam Epitaxy

The GaN columnar crystals of nanometric sizes have been grown by molecular beam epitaxy with high-frequency plasma initiation of nitrogen discharge. The types and distribution of defects in these nanostructures on the (0001) sapphire substrates are studied by transmission electron microscopy (TEM). It is revealed that inversion domains begin to form almost at the interface irrespective of the presence of an initial low-temperature buffer layer. The critical diameter of dislocation-free columns, their density, and mean sizes are determined. It is shown that the low-temperature buffer layer affects the density of dislocations, their spatial distribution, and the mean sizes of columns. The nanosizes of grown crystals suggest a further use of these crystals and the growth method for producing molecular-beam epitaxial quantum-size objects (quantum dots and wires) in a promising AlGaInN system.

MBE GaN grown on (101) NdGaO3 substrates

Abstract We investigate the structure, morphology and optical properties of gallium nitride (GaN) films deposited on (101) neodium gallate (NdGaO 3 ) substrates by molecular beam epitaxy. Scanning electron microscopy, X-ray diffraction, photoluminescence and capacity–voltage measurements are used for the films characterization. Comparison of the GaN/NdGaO 3 layer properties with those of GaN films grown on (0001) sapphire substrates has revealed the higher luminescence efficiency of the former.

X-ray diffractometric study of the influence of a buffer layer on the microstructure of molecular-beam epitaxial InN layers of different thicknesses

Thin layers of InN are grown by molecular beam epitaxy on (0001) sapphire substrates. The influence of thin (15 nm) InN buffer layers and their temperature treatment on the structural quality of the grown layers is investigated by double-crystal and triple-crystal x-ray diffractometry. It is revealed that the preliminary high-temperature (900°C) annealing of the buffer layer leads to a notable improvement in the quality of the layers grown on this buffer. The densities of vertical screw and vertical edge dislocations decrease (to 1.9×108 cm−2 and 1.3×1011 cm−2, respectively) with an increase in the distance from the interface (by ∼1 µm).

Molecular-beam epitaxy growth and characterization of 5-μm quantum cascade laser

Molecular-beam epitaxy growth of 5 um emitting strain-compensated quantum semiconductor laser (QCL) is reported. The QCL structure is characterized by complementary techniques: high-resolution X-ray diffraction and dynamical secondary-ion mass-spectrometry, that reveal the high quality of QCL structure and in-depth distribution of chemical composition, respectively.