Petr S. Kop'ev

InGaAs/GaAs Quantum Dot Lasers with Ultrahigh Characteristic Temperature (T 0= 385 K) Grown by Metal Organic Chemical Vapour Deposition

Low threshold current density (AlInGa)As/GaAs lasers based on InGaAs quantum dots (QDs) are grown by metal organic chemical vapour deposition (MOCVD). Quantum dots deposited at 490° C and covered with GaAs are directly revealed in the active region. On a transmission electron microscopy (TEM) image of the laser structure no large clusters or dislocations are found over a macroscopic distance. We show that the properties of QD lasers can be strongly improved if the QDs are confined by Al0.3Ga0.7As barriers and the cladding layers are grown at high temperature. Optimisation of the laser structure geometry allows extension of the range of ultrahigh temperature stability (T0=385 K) of the threshold current to 50° C.

Tunable laser spectroscopy of spin injection in ZnMnSe/ZnCdSe quantum structures

Magneto-optical spectroscopy in combination with tunable laser excitation is employed to study exciton spin alignment and injection in ZnMnSe/ZnCdSe quantum structures. This approach enables us to selectively create preferred spin orientation and to separately monitor subsequent spin injection from individual spin states, thus shedding light on a possible source of spin loss. It is shown that the limited spin polarization in a nonmagnetic quantum well due to spin injection from a ZnMnSe-based diluted magnetic semiconductor (DMS) is not caused by a limited degree of spin alignment in the DMS, which is in fact complete, but rather occurs during subsequent processes.

A thermodynamic analysis of the growth of III–V compounds with two volatile group V elements by molecular-beam epitaxy

Abstract We propose a thermodynamic model for molecular-beam epitaxy (MBE) growth of III–V compounds with two volatile group V elements to explain the incorporation of As and P into GaInPAs. To describe experimental results contradicting previous thermodynamic approaches, the MBE is considered as a stationary irreversible process. The effect of strain caused by lattice mismatch between the growing film and the substrate is taken into account.

Resonant spin-flip Raman scattering and localized exciton luminescence in submonolayer InAs-GaAs structures

Abstract We report on efficient resonant spin-flip Raman scattering due to localized heavy-hole excitons in single submonolayer InAs insertions in a GaAs matrix. Exciton, heavy-hole and electron g factors are directly measured for samples with different average thicknesses of InAs. The large size uniformity of the InAs islands manifests itself in very narrow heavy- and light-hole exciton photoluminescence peaks which also allow us to measure exciton g factors by magneto-luminescence spectroscopy.

Molecular beam epitaxy (MBE) growth of composite (In,Al)As/(In,Ga)As vertically coupled quantum dots and their application in injection lasers

Injection lasers based on self-organized (In,Ga)As/(Al,Ga)As quantum dots (QD) suffer from the gain saturation due to the limited amount of QD states participating in lasing. In the present work, we demonstrate the direct increase in the areal density of (In,Ga)As QDs. We used an array of (In,Al)As QDs demonstrating considerably higher density than Al-free QDs as nucleation centers for the (In,Ga)As QD formation. Finally, composite vertically coupled (In,Al)As/(In,Ga)As QDs with increased areal density are formed, which is confirmed by photoluminescence and TEM. Using the denser array of (In,Al)As/(In,Ga)As QDs in the active region of injection laser leads to the increase in modal gain, reduction in threshold current density at high mirror loss, and increase in maximum output power.

On the spin injection in ZnMnSe/ZnCdSe heterostructures

We present results from a detailed study of spin injection in thin II-VI wide band gap semiconductor heterostructures by magnetooptical spectroscopy. It is shown that efficient spin alignment can ...

Growth and Characterization of Coherent Quantum Dots Grown by Single- and Multi-Cycle Metal-Organic Chemical Vapour Deposition

Very strongly electronically coupled zero-dimensional structures were grown using metal-organic chemical vapour deposition (MOCVD). The method is based on formation of first a sheet with InGaAs pyramids on the GaAs (100) surface, and subsequent alternate short-period GaAs–InGaAs deposition with GaAs layer thickness much smaller than the pyramid height. This results in formation of column-like InGaAs structures. Each structure has a characteristic lateral size of ~23 nm at the top and is composed of many closely packed InGaAs parts separated by only 2–3 monolayer-thick GaAs barrier layers. Each upper InGaAs part in a column is progressively larger than the lower parts. The full width at half-maximum of luminescence of 28 meV at 8 K indicates good average uniformity of the electronically coupled dot ensemble. Effective tunability of the emission wavelength at and around 1.3 µ m can be realized using this approach.

Peculiarities of Neutron-Transmutation Phosphorous Doping of SiC Enriched with 30Si Isotope: Electron Paramagnetic Resonance Study

High concentration of two types of P donors up to 1017 cm-3 in SiC enriched with 30Si after neutron transmutation doping (NTD) has been achieved. It was established that annealing at sufficiently low temperature of 1300oC, that is 500-600°C lower compared with annealing of NTD SiC with natural isotope composition, gives rise to the EPR signal of shallow P donors, labeled sPc1, sPc2 and sPh. The correlated changes of the EPR spectra of the three sP centres in all the experiments and the qualitative similarities with spectra of shallow N donors prove that these centres have shallow donor levels and a similar electronic structure and belong to different lattice sites. The annealing at 1700°C results in a transformation of one type of P donors (sPc1, sPc2 and sPh) into another type having low temperature EPR spectra labeled dP.

Novel hybrid III-V/II-VI mid-infrared laser structures with high asymmetric band offset confinements

We present a novel hybrid laser structure based on III-V and II-VI compounds combining some advantages of type I and type II heterojunctions in one heterostructure. Such design allows the achievement of large energy offsets at the interface in the conduction and the valence band exceeding of 1.0 eV in order to provide good electron and hole confinement. P-AlAsSb/n-InAs/N-Cd(Mg)Se laser heterostructures were grown on p-InAs substrates by original technology of MBE method in two separate growth chambers consequently. Photoluminescence spectra included tow emission bands at hv=0.41 eV and hv=2.08 eV associated with InAs and CdMgSe bulk recombination transitions, respectively. Intense electroluminescence was observed at (lambda) =2.73micrometers (77K) and (lambda) =3.12micrometers (300K). Weak temperature dependence of spontaneous emission indicated the effective carrier confinement in the InAs layer due to large potential barriers ((Delta) sEc=1.28eV and (Delta) EV=1.68eV). Proposed hybrid III-V/II-VI heterostructure is very promising for creation the mid-infrared lasers with improved performances operating in the spectral range of 3- 5micrometers .

RT exciton waveguiding and lasing in submonolayer CdSe–(Zn, Mg)(S, Se) structures

We demonstrate exciton waveguiding and short wavelength lasing (460 nm at 300 K) in quantum dot structures based on submonolayer superlattices. High resolution electron microscopy studies reveal that CdSe submonolayer insertion in a ZnSe matrix forms an array of 2D nanoscale islands. Strong modulation in the optical reflectance spectra is observed in a 20 period submonolayer superlattice structure at energy corresponding to the localized exciton state, and the lasing occurs directly in the spectral region of the exciton-induced enhancement of the refractive index.