S. I. Troshkov

Growth and structure of GaN layers on silicon carbide synthesized on a Si substrate by the substitution of atoms: A model of the formation of V-defects during the growth of GaN

This paper presents the results of the electron microscopic study of GaN/AlGaN/AlN/SiC/Si(111) structures grown by the metal-organic vapor phase epitaxy. A SiC epitaxial buffer nanolayer has been grown by a new method of substitution of atoms on the Si(111) substrate. It has been found that there is a strong dependence of the density of dislocations and V-defects on the synthesis conditions of SiC and the thickness of the AlN layer. It has been proved experimentally that the creation of a low-temperature AlN insert with a simultaneous decrease in the thickness of the AlN layer to values of no more than 50 nm makes it possible to almost completely prevent the formation of V-defects in the GaN layer. The density of screw and mixed dislocations in the GaN layer of the studied samples lies in the range from 5 × 109 to 1 × 1010 cm−2. A theoretical model of the formation of V-defects during the growth of GaN has been developed.

Control of emission spectra in quantum dot microdisk/microring lasers

Focused ion beam is applied to quantum dot based microresonators to form pits or groove on their surface. The emission spectra of the resonators based lasers are significantly thinned out after the ion beam milling, and one or two modes become dominant instead of a group of modes having comparable intensities. The linewidth of the lasing mode is kept unchanged, whereas the lasing threshold demonstrates an insignificant growth.

Single-spatial-mode semiconductor VCSELs with a nonplanar upper dielectric DBR

Single-spatial-mode semiconductor vertical-cavity surface-emitting lasers (VCSELs) with a non-planar upper (output) dielectric distributed Bragg reflector (DBR) for the 850 nm spectral region are fabricated. The suggested design provides stable single-mode generation in the entire range of working currents, limited by overheating of the active region. Devices with intracavity contacts and a comparatively large current-aperture diameter (5–6 μm) exhibit single-mode lasing at a wavelength of 840–845 nm in the continuous-wave mode at room temperature with threshold currents of 1.2–1.3 mA, a differential efficiency of 0.5–0.55 mW mA−1, and anoutput power of up to 2 mW.

Group-III-nitride-based light-emitting diode on silicon substrate with epitaxial nanolayer of silicon carbide

A light-emitting diode (LED) structure based on group III nitride has been grown for the first time on Si(111) substrate with SiC buffer nanolayer (50- to 200-nm-thick) obtained by solid-phase epitaxy. This LED structure is characterized by record low (<108 cm−2) density of lattice misfit dislocations at a total dislocation density of ∼8 × 108 cm−2. The photo- and electroluminescence spectra of obtained structures have been measured.

High-temperature lasing in a microring laser with an active region based on InAs/InGaAs quantum dots

Lasing at a wavelength of >1.3 μm has been achieved at temperatures of up to 380 K in a ring microlaser (diameter of 6 μm) with an active region based on InAs/InGaAs quantum dots.

Thermal resistance of ultra-small-diameter disk microlasers

The thermal resistance of AlGaAs/GaAs microlasers of the suspended-disk type with a diameter of 1.7–4 μm and InAs/InGaAs quantum dots in the active region is inversely proportional to the squared diameter of the microdisk. The proportionality factor is 3.2 × 10−3 (K cm2)/W, and the thermal resistance is 120–20°C/mW.

Decreasing parasitic capacitance in vertical-cavity surface-emitting laser with selectively oxidized aperture

Results of a comparative study of the structural parameters and the static and dynamic characteristics of vertical-cavity surface-emitting lasers (VCSELs) with microresonators based on Al0.15Ga0.85As and Al0.8Ga0.2As are presented. It is established that the vertical oxidation of layers in the Al0.8Ga0.2As microresonator during formation of the current aperture leads to a significant increase in the oxide thickness. This leads to a considerable decrease in parasitic capacitance of the device and a 1.7- to 2-fold growth in the cut-off frequency of a low-frequency filter formed by parasitic elements of the equivalent electric scheme of the device.

Gallium nitride nanowires and microwires with exceptional length grown by metal organic chemical vapor deposition via titanium film

We present a new approach for synthesis of GaN nanowires and microwires by metal organic chemical vapor deposition via a thin titanium film evaporated onto sapphire substrate prior to growth. Titanium etches a two-dimensional GaN layer deposited at the initial stage and GaN nanowires subsequently emerge at the boundaries of the etched grains. These wires grow at an exceptional elongation rate of 18 μm/min and extend radially at a rate of 0.14 μm/min. The GaN layer between the wires grows at a rate of 0.1 μm/min. High material quality of these structures is confirmed by micro-photoluminescence spectroscopy. We investigate the initial nucleation stage, the time evolution of the wire length and diameter, the length and diameter distributions and speculate about a mechanism that yields the observed growth behavior.

Synthesis of GaN nano- and microwire crystals induced by a titanium nanolayer

The possibilities of a new method of growing gallium nitride nano- and microwire crystals using continuous titanium films with a thickness of 10–30 nm during growth are described. It is shown that this method can provide growth of high-quality GaN nanowire crystals at an extremely high rate of about 10 μm/min.

Electrically pumped InGaAs/GaAs quantum well microdisk lasers directly grown on Si(100) with Ge/GaAs buffer

In this work we report, to the best of our knowledge, the first quantum well electrically-pumped microdisk lasers monolithically deposited on (001)-oriented Si substrate. The III-V laser structure was epitaxially grown by MOCVD on silicon with an intermediate MBE-grown Ge buffer. Microlasers with an InGaAs/GaAs quantum well active region were tested at room temperature. Under pulsed injection, lasing is achieved in microlasers with diameters of 23, 27, and 31 µm with a minimal threshold current density of 28 kA/cm2. Lasing spectrum is predominantly single-mode with a dominant mode linewidth as narrow as 35 pm.