Igor V. Kochnev

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.

1.3 µm luminescence and gain from defect-free InGaAs-GaAs quantum dots grown by metal-organic chemical vapour deposition

Annealing of InGaAs quantum dots (QDs) fabricated by metal-organic chemical vapour deposition and covered with a very thin GaAs cap layer completely eliminates large dislocated InGaAs clusters and remarkably improves the optical properties of the structures. A modal gain of ~4 cm-1 is achieved in the 1.35 µm range. The elimination of defects allows the stacking of QDs emitting at 1.3 µm without deterioration of their optical and structural properties and reduces the QD density in the upper sheets.

Formation of coherent superdots using metal‐organic chemical vapor deposition

We demonstrate direct growth of electronically coupled zero‐dimensional structures forming a super‐quantum dot using metal‐organic chemical vapor deposition. After the first sheet with InGaAs pyramids is formed on GaAs surface, alternate short‐period GaAs‐InGaAs deposition leads to spontaneous formation of layered structures driven by the energetics of Stranski–Krastanow growth. As a result columnlike InGaAs structures each having a characteristic lateral size of ∼23 nm at the top and composed of many closely packed InGaAs parts are formed. The full width at half maximum of superdot luminescence of 28 meV at 8 K indicates good average uniformity of the superdot ensemble. Absorption is found to be resonant with luminescence.

Three-dimensional arrays of self-ordered quantum dots for laser applications

Abstract Semiconductor heterostructures with quantum dots (QDs) are experimentally proved to exhibit properties expected for zero-dimensional systems, e.g. ultrasharp luminescence lines up to high temperatures, massively increased exciton oscillator strength per unit volume and temperature insensitivity of the radiative lifetime. When applied to the injection lasers these advantages help to increase strongly material gain, differential gain, to improve temperature stability of the threshold current and to suppress chirp. Threshold current densities as low as 60 A/cm 2 at 300 K are obtained. Formation of QDs with properties satisfying device requirements on QD size, shape, uniformity and density became possible by utilizing self-ordering phenomena on crystal surfaces.

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.

Room temperature quantum dot lasers: From basic experiments to first device oriented structures

Summary form only given. Due to increasing of the quantum dot (QD) layer number up to 10 the threshold current density was reduced at RT and 85K, respectively in a quantum dot laser. Temperature dependence of the lasing wavelength and its value at RT show that such heterostructure lasers lasing via QD states. It is also proved by linear behaviour of the threshold current density vs. laser optical output losses dependence.

The influence of leakage on the characteristics of QW lasers

The paper reports on theoretical and experimental studies of the threshold current density and differential quantum efficiency dependencies on output losses for AlGaAs/GaAs and InGaAsP/GaAs SQW SCH laser diodes. A theoretical model is proposed to calculate the effect of waveguide recombination and leakage to the cladding on the threshold current and differential quantum efficiency of SQW SCH lasers. It is shown that the model assuming quasineutrality and continuity of quasi Fermi levels at interfaces gives a correct description of the process of carrier recombination in the waveguide layers of the lasers in question. Carrier leakage from the active region should be the main cause of increase of the threshold current density in the SQW lasers for densities in excess of ∼3 kA/cm2. It has been established that the carrier concentration in the waveguide increases above the lasing threshold as well, which can result in enhanced leakage into the claddings with increasing current density and to an anomalous decr...

Far-infrared spontaneous emission from quantum dot and quantum well structures accompanying near-infrared lasing

Spontaneous radiation from laser structures with quantum dots connected with hole and electron interlevel transitions was found and investigated. The radiation is observed only under simultaneous stimulated interband emission and has a similar current threshold.