InGaAs/GaAs structures with quantum dots in vertical optical cavities for wavelengths near 1.3 µm

Semiconductor heterostructures with vertical optical cavities with active regions, based on arrays of InAs quantum dots inserted in an external InGaAs quantum well, have been obtained by molecular-beam epitaxy on GaAs substrates. The dependences of the reflection and photoluminescence spectra on the structural characteristics of the active region and optical cavities have been investigated. The proposed heterostructures are potentially suitable for optoelectronic devices at wavelengths near 1.3 μm. Fiz. Tekh. Poluprovodn. 33, 629–633 (May 1999)     

Quantum light source devices of In(Ga)As semiconductor self-assembled quantum dots

A brief introduction of semiconductor self-assembled quantum dots (QDs) applied in single-photon sources is given. Single QDs in confined quantum optical microcavity systems are reviewed along with their optical properties and coupling characteristics. Subsequently, the recent progresses in In(Ga)As QDs systems are summarized including the preparation of quantum light sources, multiple methods for embedding single QDs into different microcavities and the scalability of single-photon emitting wavelength. Particularly, several In(Ga)As QD single-photon devices are surveyed including In(Ga)As QDs coupling with nanowires, InAs QDs coupling with distributed Bragg reflection microcavity and the In(Ga)As QDs coupling with micropillar microcavities. Furthermore, applications in the field of single QDs technology are illustrated, such as the entangled photon emission by spontaneous parametric down conversion, the single-photon quantum storage, the chip preparation of single-photon sources as well as the single-photon resonance-fluorescence measurements.     

Strain tunable quantum dot based non-classical photon sources

Semiconductor quantum dots are leading candidates for the on-demand generation of single photons and entangled photon pairs.High photon quality and indistinguishability of photons from different sources are critical for quantum information applications.The inability to grow perfectly identical quantum dots with ideal optical properties necessitates the application of post-growth tuning techniques via e.g.temperature,electric,magnetic or strain fields.In this review,we summarize the state-of-the-art and highlight the advantages of strain tunable non-classical photon sources based on epitaxial quantum dots.Using piezoelectric crystals like PMN-PT,the wavelength of single photons and entangled photon pairs emitted by InGaAs/GaAs quantum dots can be tuned reversibly.Combining with quantum light-emitting diodes simultaneously allows for electrical triggering and the tuning of wavelength or exciton fine structure.Emission from light hole exciton can be tuned,and quantum dot containing nanostructure such as nanowires have been piezo-integrated.To ensure the indistinguishability of photons from distant emitters,the wavelength drift caused by piezo creep can be compensated by frequency feedback,which is verified by two-photon interference with photons from two stabilized sources.Therefore,strain tuning proves to be a flexible and reliable tool for the development of scalable quantum dots-based non-classical photon sources.     

1.3 µm vertical microcavities with InAs/InGaAs quantum dots and devices based on them

Various structures with optical microcavities and active layers based on InGaAs/GaAs quantum dots MBE-grown on GaAs substrates were studied theoretically and experimentally. LEDs for the 1.3 μm spectral range with narrow spectral characteristics and low light beam divergence were fabricated. Vertical lasing at 1.3 μm was obtained in a structure with oxidized AlO/GaAs mirrors under injection pumping. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 7, 2001, pp. 889–895. Original Russian Text Copyright ? 2001 by Sakharov, Krestnikov, Maleev, Kovsh, Zhukov, Tsatsul’nikov, Ustinov, Ledentsov, Bimberg, Lott, Alferov.     

Lasing at a wavelength close to 1.3 µm in InAs quantum-dot structures

The feasibility of lasing at a wavelength close to 1.3 μm is demonstrated in InAs quantum-dot structures placed in an external InGaAs/GaAs quantum well. It is shown that the required wavelength can be attained with the proper choice of thickness of the InAs layer deposited to form an array of three-dimensional islands and with a proper choice of mole fraction of InAs in the InGaAs quantum well. Since the gain attained in the ground state is insufficient, lasing is implemented through excited states in the temperature interval from 85 K to 300 K in a structure based on a single layer of quantum dots. The maximum attainable gain in the laser structure can be raised by using three rows of quantum dots, and this configuration, in turn, leads to low-threshold (70 A/cm²) lasing through the ground state at a wavelength of 1.26 μm at room temperature. Fiz. Tekh. Poluprovodn. 33, 1020–1023 (August 1999)     

InGaAs/InP heterostructures with strained quantum wells and quantum dots (λ=1.5–1.9 µm)

Strongly strained In_xGa_1−x As/In_0.53Ga_0.47As/InP heterostructures with indium content x=0.69−1.0 in the active region were investigated experimentally and theoretically. Two types of structures were obtained by vapor-phase epitaxy from metalorganic compounds: 1) with isolated compression-strained quantum wells and 2) with self-organized nanosize InAs clusters (quantum dots). The temperature dependence of the quantum radiation efficiency of samples with quantum wells in the temperature range 77–265 K is characterized by T ₀=43 K. One reason for the low value of T ₀ is electron delocalization in the active region. The maximum radiation wavelength obtained in structures with quantum dots is 1.9 μm at 77 K. Fiz. Tekh. Poluprovodn. 33, 1105–1107 (September 1999)     

Optical and structural properties of InAs quantum dot arrays grown in an InxGa1−x As matrix on a GaAs substrate

Structural and optical properties of InAs quantum dots (QDs) deposited on the surface of a thick InGaAs metamorphic layer grown on a GaAs substrate have been studied. The density and lateral size of QDs are shown to increase in comparison with the case of QDs grown directly on a GaAs substrate. The rise of In content in the InGaAs layer results in the red shift of the photoluminescence (PL) line, so that with 30 at % indium in the metamorphic layer the PL peak lies at 1.55 μm. The PL excitation spectroscopy of the electronic spectrum of QDs has shown that the energy separation between the sublevels of carriers in QDs decreases as the In content in the InGaAs matrix increases. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 7, 2004, pp. 867–871. Original Russian Text Copyright ? 2004 by Kryzhanovskaya, Gladyschev, Blokhin, Musikhin, Zhukov, Maksimov, Zakharov, Tsatsul’nikov, Ledentsov, Werner, Guffart, Bimberg.     

Design and technology of vertical-cavity surface-emitting lasers with nonconducting epitaxial mirrors

Design and technology problems in the fabrication of vertical-cavity surface-emitting lasers (VCSELs) equipped with nonconducting distributed Bragg reflectors (DBRs) and fabricated using molecular-beam epitaxy are considered. VCSELs with an active region were formed on the basis of InGaAs quantum wells and incorporated an AlGaAs/GaAs bottom DBR and an oxidized AlGaO/GaAs top DBR; the diameter of the oxidized aperture was equal to 7–12 μm. The devices exhibit a continuous-wave lasing at room temperature with threshold currents of 0.5–1.5 mA, a differential efficiency as high as 0.5 mW/mA, and a highest output power of 3 mW. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 10, 2003, pp. 1265–1269. Original Russian Text Copyright ? 2003 by Maleev, Kovsh, Zhukov, Vasil’ev, Mikhrin, Kuz’menkov, Bedarev, Zadiranov, Kulagina, Shernyakov, Shulenkov, Bykovskii, Solov’ev, M?ller, Ledentsov, Ustinov.     

Resonant cavity enhanced photoluminescence of tensile strained Ge/SiGe quantum wells on silicon-on-insulator substrate

The tensile strained Ge/SiGe multiple quantum wells （MQWs） grown on a silicon-on-insulator （SOI） substrate were fabricated successfully by ultra-high chemical vapor deposition. Room temperature direct band photoluminescence from Ge quantum wells on SOI substrate is strongly modulated by Fabry-Perot cavity formed between the surface of Ge and the interface of buried SiO2. The photoluminescence peak intensity at 1.58 μm is enhanced by about 21 times compared with that from the Ge/SiGe quantum wells on Si substrate, and the full width at half maximum （FWHM） is significantly reduced. It is suggested that tensile strained Ge/SiGe multiple quantum wells are one of the promising materials for Si-based microcavity lijzht emitting devices.     

Photo-and electroluminescence in the 1.3-µm wavelength range from quantum-dot structures grown on GaAs substrates

A method is proposed to increase the emission wavelength from structures grown on GaAs substrates by inserting a strained InAs quantum dot array into an external InGaAs quantum well. The dependence of the luminescence peak position on the active region design was investigated for structures grown by this method. Room-temperature photo-and electroluminescence spectra in the 1.3-μm wavelength range are compared. Fiz. Tekh. Poluprovodn. 33, 180–183 (February 1999)     

Electrically driven single-photon sources

Single-photon sources are building blocks for photonic quantum information processes. Of the many single-photon generation schemes, electrically driven single-photon sources have the advantages of realizing monolithic integration of quantum light sources and detectors without optical filtering, thus greatly simplify the integrated quantum photonic circuits. Here, we review recent advances on electrically driven single-photon sources based on solid-state quantum emitters, such as semiconductor epitaxial quantum dots, colloidal quantum dots, carbon nanotubes, molecules, and defect states in diamond, SiC and layered semiconductors. In particular, the merits and drawbacks of each system are discussed. Finally, the article is concluded by discussing the challenges that remain for electrically driven single-photon sources.     

Investigation of the device characteristics of a low-threshold quantum-dot laser emitting at 1.9 µm

InAs quantum dots in a InGaAs matrix grown on an InP substrate by molecular-beam epitaxy are employed as the active region of an injection laser. Lasing via quantum-dot states is observed in the temperature range 77–200 K. At the lowest threshold current density 11 A/cm² the radiation wavelength is equal to 1.894 μm (77 K). Fiz. Tekh. Poluprovodn. 32, 892–895 (July 1998)     

VCSELs based on arrays of sub-monolayer InGaAs quantum dots

Vertical-cavity surface-emitting lasers (VCSELs) with an active region based on sub-monolayer InGaAs quantum dots and doped AlGaAs/GaAs distributed Bragg reflectors were grown by MBE. VCSELs with current aperture of 3 μm in diameter demonstrate single-mode lasing in 980-nm range with the threshold current of 0.6 mA, maximum output power up to 4 mW, and external differential efficiency of 68%. Multimode VCSELs with a (10–12)-μm aperture demonstrate ultralow internal optical loss of 0.09% per pass, which compares favorably with the best results obtained in similar lasers with undoped distributed Bragg reflectors. Original Russian Text ? S.A. Blokhin, N.A. Maleev, A.G. Kuz’menkov, Yu. M. Shernyakov, I.I. Novikov, N.Yu. Gordeev, V.V. Dyudelev, G.S. Sokolovskiĭ, V.I. Kuchinskiĭi, M.M. Kulagina, M.V. Maximov, V.M. Ustinov, A.R. Kovsh, S.S. Mikhrin, N.N. Ledentsov, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 633–638.     

High-power 1.5 µm InAs-InGaAs quantum dot lasers on GaAs substrates

Light-current, spectral, and temperature characteristics of long-wavelength (1.46–1.5 μm) lasers grown on GaAs substrates, with an active area based on InAs-InGaAs quantum dots, are studied. To reach the required lasing wavelength, quantum dots were grown on top of a metamorphic InGaAs buffer layer with an In content of about 20%. The maximum output power in pulsed mode was 7 W at room temperature. The differential efficiency of the laser, which had a 1.5-mm-long cavity, was 50%. The temperature dependence of the threshold current is described by a characteristic temperature of 61 K in the temperature range 10–73°C. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 6, 2004, pp. 763–766. Original Russian Text Copyright ? 2004 by Maksimov, Shernyakov, Kryzhanovskaya, Gladyshev, Musikhin, Ledentsov, Zhukov, Vasil’ev, Kovsh, Mikhrin, Semenova, Maleev, Nikitina, Ustinov, Alferov.     

Heteroepitaxial growth of InAs on Si: A new type of quantum dot

The mechanism for heteroepitaxial growth in the InAs/Si system is studied by reflection highenergy electron diffraction, scanning tunnelling microscopy, and photoluminescence. For certain growth conditions, InAs nanostructures are found to develop on the Si surface immediately during the growth process in the course of molecular beam epitaxy. The range of substrate temperatures that lead to formation of nanosized islands is determined. InAs quantum dots grown on a buffer Si layer with a silicon layer of thickness 50 nm grown on the top produced photoluminescence lines at a wavelength of 1.3 μm at 77K and 1.6 μm at 300 K. Fiz. Tekh. Poluprovodn. 33, 1066–1069 (September 1999)     

TE- and TM-polarized optoelectronic properties of HgCdTe quantum wells

A systematic investigation of the strength of TE-polarized and TM-polarized intersubband and interband transitions in narrow-gap HgCdTe quantum wells is performed using an eight-band finite-element k·p formalism. Effects of varying the well composition, well width, and applied electric field are explored for both polarizations, and the possibility of fabricating low-threshold quantum cascade lasers using this system is pointed out. Especially promising are the prospects for optically-pumped terahertz lasers based on interband transitions. Lasers emitting in the 30–45 μm wavelength range (falling in the phonon bands of III–V quantum wells), are projected to operate above liquid-nitrogen temperature.     

Indium arsenide light-emitting diodes with a cavity formed by an anode contact and semiconductor-air interface

Room-temperature spectral characteristics of light-emitting diodes that are based on double InAsSbP/InAs heterostructures with an active InAs layer and a cavity formed by a wide anode contact and the structure surface and that emit near 3.3 μm are considered. The far-field pattern and the mode structure of light-emitting diodes 7.5–45 μm thick are reported, as well as the dependences of the mode position on the pump current. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 10, 2004, pp. 1270–1274. Original Russian Text Copyright ? 2004 by Zotova, Il’inskaya, Karandashev, Matveev, Remennyi, Stus’, Shustov.     

Stacked InAs/InGaAs quantum dot heterostructures for optical sources emitting in the 1.3 µm wavelength range

A method is proposed for growing stacked InAs/InGaAs self-organized quantum dots on GaAs substrates. The technique allows fabrication of structures exhibiting intense and narrow-line photoluminescence in the 1.3 μm wavelength region. The influence of growth conditions on structural and optical characteristics was studied. The proposed structures show promise in developing vertical-cavity surface-emitting devices. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 5, 2000, pp. 612–616. Original Russian Text Copyright ? 2000 by Maleev, Zhukov, Kovsh, Mikhrin, Ustinov, Bedarev, Volovik, Krestnikov, Kayander, Odnoblyudov, Suvorova, Tsatsul’nikov, Shernyakov, Ledentsov, Kop’ev, Alferov, Bimberg.     

Controllable growth of GeSi nanostructures by molecular beam epitaxy

We present an overview on the recent progress achieved on the controllable growth of diverse GeSi alloy nanostructures by molecular beam epitaxy. Prevailing theories for controlled growth of Ge nanostructures on patterned as well as inclined Si surfaces are outlined firstly, followed by reviews on the preferential growth of Ge nanoislands on patterned Si substrates, Ge nanowires and high density nanoislands grown on inclined Si surfaces, and the readily tunable Ge nanostructures on Si nanopillars. Ge nanostructures with controlled geometries, spatial distributions and densities, including two-dimensional ordered nanoislands, three-dimensional ordered quantum dot crystals, ordered nanorings, coupled quantum dot molecules, ordered nanowires and nanopillar alloys, are discussed in detail. A single Ge quantum dot-photonic crystal microcavity coupled optical emission device demonstration fabricated by using the preferentially grown Ge nanoisland technique is also introduced. Finally, we summarize the current technology status with a look at the future development trends and application challenges for controllable growth of Ge nanostructures.     

Power conversion efficiency of quantum dot laser diodes

The power conversion efficiency of laser diodes with an array of quantum dots in the active region is analyzed. A model is proposed which allows analytical determination of the optimal cavity length corresponding to the highest conversion efficiency for a given output power. A comparison is made with experimental data for high-power lasers based on submonolayer quantum dots emitting at 0.94 μm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 5, 2000, pp. 628–632. Original Russian Text Copyright ? 2000 by Zhukov, Kovsh, Mikhrin, Maleev, Odnoblyudov, Ustinov, Shernyakov, Kondrat’eva, Livshits, Tarasov, Ledentsov, Kop’ev, Alferov, Bimberg.