A. M. Mintairov

Volmer–Weber and Stranski–Krastanov InAs-(Al,Ga)As quantum dots emitting at 1.3 μm

Quantum dots (QDs) formed on GaAs(100) substrates by InAs deposition followed by (Al,Ga)As or (In,Ga,Al)As overgrowth demonstrate a photoluminescence (PL) peak that is redshifted (up to 1.3 μm) compared to PL emission of GaAs-covered QDs. The result is attributed to redistribution of InAs molecules in the system in favor of the QDs, stimulated by Al atoms in the cap layer. The deposition of a 1 nm thick AlAs cover layer on top of the InAs–GaAs QDs results in replacement of InAs molecules of the wetting layer by AlAs molecules, leading to a significant increase in the heights of the InAs QDs, as follows from transmission electron microscopy. This effect is directly confirmed by transmission electron microscopy indicating a transition to a Volmer–Weber-like QD arrangement. We demonstrate an injection laser based on this kind of QDs.

Effect of dislocation scattering on the transport properties of InN grown on GaN substrates by molecular beam epitaxy

The authors report the structural, optical, and transport properties of high quality InN epitaxial films grown on GaN substrates by plasma-assisted molecular beam epitaxy. They have found a strong correlation between the structural quality and the measured carrier mobilities. Comparison of temperature-dependent Hall data with a theoretical transport model indicates that the electron mobility in state-of-art InN is limited by charged dislocation scattering. The model predicts that an order-of-magnitude increase in electron mobilities can be achieved by the reduction of dislocation densities in InN.

Order–disorder transition in epitaxial ZnSnP2

We report on the growth of ZnSnP2 on GaAs(100) substrates by gas source molecular beam epitaxy. Samples were grown in the temperature range of 300–360 °C. A small change in the Sn/Zn flux ratio at constant substrate temperature was found to result in a transition from a lattice mismatched, Δa/a∼0.4%–0.7%, disordered crystal structure to a lattice matched, ordered chalcopyrite structure. Infrared reflectance and Raman measurements were used to monitor this phase transition. Formation of the two different crystal modifications is discussed in terms of vapor–solid and vapor–liquid–solid growth modes.

Transport anisotropy in spontaneously ordered GaInP2 alloys

Large anisotropy in minority carrier diffusion length and specific conductivity is observed in epitaxial layers of GaInP2 alloys with CuPtB-type ordering. Both the diffusion length and specific conductivity are enhanced, by factor of 10, in the [110] direction, parallel to the line of intersection of the ordered (1–11) and (−111) planes with the (001) growth surface. The reduction in transport length in the [1–10] direction is attributed to carrier scattering at domain boundaries. No transport anisotropy is observed in disordered GaInP2 epitaxial layers.

Infrared spectroscopy of ZnSiN2 single-crystalline films on r-sapphire

This letter presents a study of optical phonon modes of single-crystalline orthorhombic ZnSiN2 semiconductor epitaxially deposited on r-sapphire. An epitaxial relationship for ZnSiN2 film was found from x-ray diffraction to be (0k0)ZnSiN2‖(10 12)Al2O3 and [100]ZnSiN2‖(1210)Al2O3. Six B1 optical modes were revealed in 400–1000 cm−1 range in s-polarized infrared reflectance spectra. This is consistent with the analysis of the phonon symmetry and selection rules presented. The frequencies of the transversal and longitudinal components, phonon damping, and oscillator strengths of the B1 phonons as well as high frequency dielectric constant e∞xx of the orthorhombic ZnSiN2 were determined.

Quantum dot lasers and relevant nanoheterostructures

Spectral and power characteristics of QD stripe lasers operating in two-state lasing regime have been studied in a wide range of operation conditions. It was demonstrated that neither self-heating nor increase of the homogeneous broadening are responsible for quenching of the ground-state lasing beyond the two-state lasing threshold. It was found that difference in electron and hole capture rates strongly affects light-current curve. Modulation p-type doping is shown to enhance the peak power of GS lasing transition. Microring and microdisk structures (D = 4-9 μm) comprising 1.3 μm InAs/InGaAs quantum dots have been fabricated and studied by μ-PL and NSOM. Ground-state lasing was achieved well above root temperature (up to 380 K). Effect of inner diameter on threshold characteristics was evaluated.

Influence of Si–N complexes on the electronic properties of GaAsN alloys

We have investigated the influence of Si–N complexes on the electronic properties of GaAsN alloys. The presence of Si–N complexes is suggested by a decrease in carrier concentration, n, with increasing N-composition, observed in GaAsN:Si films but not in modulation-doped heterostructures. In addition, for GaAsN:Te (GaAsN:Si), n increases substantially (minimally) with annealing-T, suggesting a competition between annealing-induced Si–N complex formation and a reduced concentration of N-related traps. Since Si–N complex formation is enhanced for GaAsN:Si growth with the (2×4) reconstruction, which has limited group V sites for As–N exchange, the (Si–N)As interstitial pair is identified as the dominant Si–N complex.

Room-temperature lasing in microring cavities with an InAs/InGaAs quantum-dot active region

Microring cavities (diameter D = 2.7–7 μm) with an active region based on InAs/InGaAs quantum dots are fabricated and their characteristics are studied by the microphotoluminescence method and near-field optical microscopy. A value of 22 000 is obtained for the Q factor of a microring cavity with the diameter D = 6 μm. Lasing up to room temperature is obtained in an optically pumped ring microlaser with a diameter of D = 2.7 μm.

Study of tunneling transport of carriers in structures with an InGaN/GaN active region

Properties of light-emitting structures with an InGaN/GaN active region emitting in a range of 500–550 nm are studied. Photoluminescence of the structures is studied at various values of external bias and temperature as well as with time resolution. With the reverse bias, a decrease in the carrier lifetime associated with tunneling exit of the carriers from the active region is found. The mechanism of tunneling leakage is simulated allowing for the Boltzmann distribution of carriers by energy; it is shown that the calculated and experimental dependences agree well. It is shown that the tunneling transport exerts a considerable effect on the characteristics of structures with an InGaN/GaN active region.

Dual optical marker Raman characterization of strained GaN-channels on AlN using AlN/GaN/AlN quantum wells and 15N isotopes

This work shows that the combination of ultrathin highly strained GaN quantum wells embedded in an AlN matrix, with controlled isotopic concentrations of Nitrogen enables a dual marker method for Raman spectroscopy. By combining these techniques, we demonstrate the effectiveness in studying strain in the vertical direction. This technique will enable the precise probing of properties of buried active layers in heterostructures, and can be extended in the future to vertical devices such as those used for optical emitters, and for power electronics.