Zhores I. Alferov

Quantum dot lasers

We presents both edge emitting and surface emitting quantum dot laser research. Growth is by both MOCVD and MBE.

Continuous-wave operation of long-wavelength quantum-dot diode laser on a GaAs substrate

Continuous-wave operation near 1.3 /spl mu/m or a diode laser based on self-organized quantum dots (QDs) on a GaAs substrate is demonstrated. Multiple stacking of InAs QD planes covered by thin InGaAs layers allows us to prevent gain saturation and achieve long-wavelength lasing with low threshold current density (90-105 A/cm/sup 2/) and high output power (2.7 W) at 17/spl deg/C heatsink temperature. It is thus confirmed that QD lasers of this kind are potential candidates to substitute InP-based lasers in optical fiber systems.

Negative characteristic temperature of InGaAs quantum dot injection laser

The range of negative characteristic temperatures in temperature dependences of threshold current density of low-threshold (In, Ga)As/(Al, Ga)As quantum dot injection lasers has been observed. A model describing the decrease in threshold current density with temperature at low temperatures is proposed.

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.

Gain and threshold characteristics of long wavelength lasers based on InAs/GaAs quantum dots formed by activated alloy phase separation

Experimental and theoretical study was made of injection lasers based on InAs/GaAs quantum dots (QDs) formed by the activated alloy phase separation and emitting at about 1.3 /spl mu/m. Electroluminescence and gain spectra were investigated. The maximum modal gain is measured experimentally using two different techniques. Threshold current densities as low as 22 A cm/sup -2/ per QD sheet were achieved. A step-like switch from ground- to excited-state transition lasing was observed with an increasing cavity loss. The characteristic temperatures for a sample with four cleaved sides and a 2-mm long stripe device at 300 K were 140 and 83 K, respectively. Single lateral-mode continuous-wave (CW) operation with the maximum output power of 210 mW was realized. Threshold characteristics of a laser were simulated taking into account radiative recombination in QDs, the wetting layer, and the optical confinement layer. The dependence of the threshold current density on the cavity length was shown to be extremely sensitive to the QD-array parameters determining the maximum gain for ground- and excited-state transitions and to the waveguide design. Our analysis reveals that nonradiative recombination channels may play an important role in the laser operation.

Progress in Quantum Dot Lasers : 1100 nm, 1300 nm, and High Power Applications

Quantum dot (QD) lasers have decisive advantages compared to quantum well lasers. Zero-dimensional charge carrier localization and reduction of charge carrier diffusion result in reduced non-radiative surface recombination and thus possibly reduced facet overheating and larger catastrophic optical damage (COD) threshold, crucial for high power operation. The emission wavelengths of 1100 nm?1300 nm are easily realized using QDs on GaAs substrate, not available with traditional quantum wells of the same material system. We present results on metal-organic chemical vapor phase deposition (MOCVD) and molecular beam epitaxy (MBE) grown high power QD lasers (up to 4 W front facet cw) based on InGaAs QDs on GaAs substrate

Self-Organized InGaAs Quantum Dots for Advanced Applications in Optoelectronics

We report on the fabrication of quantum dot (QDs) heterostructures for applications in optoelectronics. Different kinds of QDs are currently used: (i) three-dimensional quantum dots obtained by Stranski-Krastanow or Volmer-Weber growth in the InAs–GaAs material system, (ii) two-dimensionally-shaped QDs formed by submonolayer insertions in the InAs–GaAs and similar systems, (iii) GaAs QDs formed on a corrugated (311)A AlAs surface, (iv) and QDs obtained by spinodal decomposition and activated spinodal decomposition in InGaAs–GaAs and InGaAsN–GaAs material systems. Formation of uniformly sized and shaped QDs is possible in all of these approaches and is mostly governed by thermodynamics. Ultrahigh modal gain and giant optical nonlinearity can be achieved in dense arrays of very small QDs. Long wavelength (1.3–1.6 µm) emission can be achieved using large InAs QDs. Recent advances in growth have made possible the realization of GaAs 1.3 µm continuous wave (CW) vertical-cavity surface-emitting lasers (VCSELs) with ~ 0.8 mW output power and long operation lifetime.

Vertically coupled quantum dot lasers: First device oriented structures with high internal quantum efficiency

Main mechanisms of internal carrier losses and leakage from the ground state of quantum dots have been studied in heterostructure lasers based on vertically coupled quantum dots. It has been shown that the threshold current density may be reduced down to 15 A/cm 2 at room temperature by reducing the non-radiative recombination and improving the carrier localization.

The double heterostructure: the concept and its applications in physics, electronics, and technology (Nobel lecture).

The art and science of heterostructure design has not remained still since its founding: While the theoretical principles initially advanced rapidly, experimental realization initially lagged until the ideal AlGaAs solid solutions were found. From this point, development into application proceeded apace. In this Review, these intial steps and the current position of heterostructure applications are surveyed. New developments, such as the inclusion of quantum dots into heterostructures-with its concomitant world-record threshold current for laser activity-and future challenges are also elucidated.

Heterostructures for Optoelectronics: History and Modern Trends

Semiconductor revolution of the 20th century determined not only technological, but also social development of the modern society. The precursors of modern semiconductor electronics were Oleg Losevs discoveries of “crystadine” and “light-emitting diode (LED)” nearly 100 years ago. Creation of the transistor and semiconductor laser and LED based on the homo p-n structure became the most decisive step. Semiconductor optoelectronics was born with the creation of GaAs and GaAsP lasers and “LED.” The possibility to control the type and level of conductivity and injection in p-n junctions was the seed from which semiconductor electronics developed. Heterostructures-“man-made crystals”-solved a more general problem: the necessity to control electron and photon fluxes in crystals. The development of physics and technology for semiconductor heterostructures resulted in drastic changes in our everyday life. It is hardly possible to imagine our recent life without double-heterostructure (DH) laser-based telecommunication systems, without efficient DH LEDs, heterostructure bipolar transistors, and high electron mobility transistors (HEMTs) for high-frequency applications. DH lasers were introduced in every household with CD players. Heterostructure solar cells have been widely used for space and terrestrial applications. The first proposals for heterostructures in semiconductor devices were made as early as in the 1950s, but the most important experimental results were received at the end of the 1960s when the first ideal AlGaAs heterostructures and low threshold room-temperature lasers, efficient heterostructure LEDs, and solar cells were created. Later semiconductor heterostructure became laboratories of low-dimension electron gases. Molecular-beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) technologies were the basis for the development of new structures, including superlattices, and for the industrial production of a large family of heterostructure semiconductor devices. Quantum dot (QD)-based optoelectronics as a modern trend in optoelectronics is the subject of a more detailed consideration.