[Zhukov Et Al., 2005]

Epitaxial growth of quantum-dot heterostructureson metamorphic buffers

Alexey Zhukov*, Alexey Vasilyev, Elizaveta Semenova, Natailia Kryzhanovskaya,Andrey Gladyshev, Mikhail Maximov, Victor Ustinov, and Nikolai Ledentsov

A. F. loffe Physico-Technical Institute, 26 Politekhnicheskaya St., 193021 St. Petersburg, Russia

ABSTRACT

Recent achievements in self-organized quantum dots (QDs) have demonstrated their potential for long-wavelength laserapplications. However, the wavelength of QD structures pseudomorphically grown on GaAs substrate is typically notlonger than 1 .3 tm. In this work we study a novel approach for extension of the spectral range of GaAs-based diodelasers up to 1.5 jtm. We use a sensitivity of QD emission to the band gap energy of surrounding matrix. The method isbased on formation of a QD array inside a metamorphic InGaAs epilayer. Growth regimes of metamorphic buffer thatenable mirror-like surface morphology in combination with effective dislocation trapping are discussed. Structural andoptical properties of metamorphic InAs/InGaAs QDs are presented. It is shown that the wavelength of QD emission canbe controllably tuned in the 1.371.58 tm range by varying the composition of metamorphic InGaAs matrix. Details offormation, fabrication, and characterization of metamorphic-based diode lasers are also presented. We demonstrate alasing wavelength as long as 1.48 jtm in the 2080 C temperature interval. The minimum threshold current density is800 A/cm2 at RT. The external differential efficiency and pulsed power maximum exceed 50%and 7 W, respectively.

Keywords: Epitaxy, metamorphic structure, quantum dots, diode laser

1. INTRODUCTION

In the standard silica fiber there are three spectral windows of low attenuation around 0.85, 1 .3, and 1 .55 tm. Theattenuation on the given wavelength sets the maximum distance for optical fiber communication. The lowest attenuationand the longest distance about 100 km are achieved for the 1.5-tm window. In shorter distances the dispersion, i.e.dependence of the refractive index on the wavelength in the fiber, is more important parameter because it affects themaximum speed of transmission. Because zero dispersion takes place at 13 lOnm, the 1 .3-tm window is ideal for high-speed transmission over optical fiber for several kms. Thus, 1 .31 .55-trn laser sources are required for optical fibercommunication.

Epitaxial growth of the laser structure can be done in the easiest form if all the layers ofthe structure are lattice-matchedto the substrate. Between InP and GaAs, two most common materials for crystalline substrates, only InP has lattice-matched alloys of suitable band gap energy. On the other hand, GaAs-based laser structures hold several advantages overhiP. First of all, it is lower price of GaAs substrates in combination with their larger diameter and lower etch-pit density.Also, AlAs/GaAs combination is well known as a perfect solution for mirrors of the surface-emitting laser. Anotheradvantage of GaAs-based structures is better electron confmement owing to larger bandedge discontinuities in thesematerials and better thermal conductivity. All this should result in better laser characteristics especially at elevatedtemperatures making it possible an uncooled laser operation.

2. SELF-ORGANIZED QUANTUM DOTSLattice-mismatched growth is the only possibility to reach sufficiently long wavelength for GaAs-based materials. Ifhighly mismatched material is deposited on substrate, like InAs on GaAs, the film is mechanically strained. It was found*E..majl. [email protected]

Optical Materials and Applications, edited by Arnold Rosental, Proceedings of SPIE Vol. 5946(SPIE, Bellingham, WA, 2005) 0277-786X/05/$15 doi: 10.1117/12.639319

Proc. of SPIE Vol. 5946 594616-1

that strain accumulation in the film leads to spontaneous transformation from layer-by-layer to island growth mode assoon as InAs thickness exceeds 1 .7 monolayers The onset of island growth mode can be easily monitored bycharacteristic transformation of reflection high-energy electron diffraction (RHEED) pattern from streaky to spotty.These InAs islands covered by GaAs are known as self-organized quantum dots (QDs).2

From the very beginning of study QDs were considered as a potential candidate for long-wavelength lasing on GaAs.Fig. 1 shows the dependence of QD peak position (solid circles) and intensity of QD line (open circles) on the amount ofInAs deposited as observed in photoluminescence (PL) at RT.3 The x-axis scale nearly corresponds to the range ofdislocation-free growth. As the QD formation takes place at 1.7 ML PL peak shifts significantly to longer wavelengths.Further deposition of InAs leads to additional red shift and emission wavelength as long as 1.2 im can easily beachieved on GaAs. Attractive advantage is that the PL intensity is still rather bright contrary to the quantum-well (QW)case where special methods should be applied to reach this spectral range (for review see Ref. 4).

0Cti

.

Possible long-wavelength application is not the only motivation for laser application of QDs. Another important aspect isassociated with intrinsic electronic structure of QD ensemble which effects on device performance.5. Briefly speaking,threshold current depends on density of electronic states in the laser active region. Minimum possible threshold currentdensity estimated for QW laser is about 50 A/cm2 at RT. Also, QW threshold current increases with increasingtemperature. At the same time, for typical density of self-organized QDs the estimated value is one order of magnitudelower, as low as 5 A/cm2. Important note is that the threshold is temperature independent because the energy width ofQD density of states is much narrower than the thermal energy.

This intrinsic property of QD array makes it very promising for laser application. The record-low threshold currentdensities about 20 A/cm2 have been already reported (for review see Ref 6). Also, temperature-independent behavior ofthe laser threshold (infinite characteristic temperature) has been recently demonstrated for QD laser operating up to80 0C7

There are several methods for increasing the wavelength of QD emission (for review see Refs. 4 and 6). Our approach isthe following: QD emission line shifts to longer wavelengths if the band gap energy of surrounding matrix is reduced 8InGaAs external QW is used instead of conventional GaAs matrix. Of course, additional care is required in this methodbecause both QD and QW materials are lattice-mismatched with respect to GaAs. At the same time, PL peak can becontrollably tuned in a wide wavelength range by changing the In mole fraction in the QW, see Fig. 2. Wavelength canreach the required 1.3-tm window without any degradation of PL intensity. Another attractive advantage of this methodis that the QD density is practically unchanged. Thus, the optical gain does not decrease.

1200

1100

49 10004)900

Figure 1. Peak position (solid circles) and PL intensity (opencircles) of InAs/GaAs quantum, dot (PL at 300 K) against theeffective thickness of InAs.

InAs effective thickness Q1A' '1L

$C)4)

Figure 2. Evolution of QD emission line with changing the Inmole fraction, x, in capping InGaAs quantum well (QW width4nm).

Wavelength, pm


3. CONCEPT OF METAMORPHIC QUANTUM-DOT LASERFigure 3 shows the experimental dependence of the wavelength of QD emission on the band gap of surrounding matrix.Different matrix band gap supposes different materials. Before this study three possible materials on GaAs substratewere known: pure bulky GaAs, bulky AlGaAs,9 and strained InGaAs QW. Also QDs in InGaAs matrix lattice-matchedto InP substrates were studied.' For a given matrix material, the QD wavelength can be slightly changed by changing theeffective thickness of deposited InAs. At the same time, changing the matrix band gap provides much wide range oftunability: from 1 im in the case ofAlGaAs up to 2 im for QDs on InP.

20\' ' I I I I

InGaAs/InP

18Oi

MM InGaAs QW16OOf t\. \ MMInGaAs Wavelength band of01 1400, .

fiber-optic communication

---!:..)fc: \ AlGaAsc :/ \1200 . InGaAs/GaAs QW \......J I ' '\GaAs\OJ o1000 I I . I .

800 1000 1200 1400 1600 1800Matrix bandgap, rneV

Figure 3. Wavelength of emission for InAs QDs embedded in different surrounding matrixes. Metamorphic matrices (MM, shown bysolid circles) are discussed in Sec. 5. Two horizontal lines mark the spectral interval suitable for fiber-optic communication.

However, there is a gap in possible matrix band gap, near 1 .01 .1 eV, because no suitable material is available. Thiswavelength interval is most interesting for optical fiber communication. Mentioned QDs in pseudomorphic InGaAs QWonly touch this region near 1 .3 tm. Further increase of In mole fraction in the QW results in plastic strain relaxation. Weconsider a possibility to achieve sufficiently narrow band gap matrix for QD formation using the concept of metamorphicgrowth.1'

A possibility to exploit metamorphic growth mode for the long-wavelength lasers has not been studied in detail yet inspite of the fact that such an approach is currently widely used for high-electron mobility transistor (HEMT) structures(see, e.g. 12) A virtual substrate, which has larger lattice parameters and lower band gap energy as compared to theGaAs, can be created by the deposition of sufficiently thick transient InGaAs buffer on initial GaAs substrate. Purpose ofthe buffer is to change the lattice parameter from GaAs to InGaAs and simultaneously block all the dislocations inside.In ideal case the strain relaxation proceeds by misfit dislocations, which propagate along the interface. The subsequentlayers ofthe structure can be dislocation-free and, thus, be suitable for light-emitting devices.

Metamorphic approach allows one to extend the spectral range of QD structures grown on GaAs substrates using thesensitivity of QD wavelength to the band gap of surrounding material. Figure 4 shows the compositional dependence ofthe band gap for In(AL,,Ga,_ p),-As quaternary alloy assuming unstrained case. For In mole fraction, x, about 2025%the band gap interval from 1.1 to 1.8 eV can be covered by changing the Al subfraction, y. This wide range provides bothsufficiently narrow band gap matrix for QD formation (InGaAs) and effective prevention of current leakage when usingInGaAIAs cladding layers (y>0.3). A comparison ofthe band diagrams ofthe 1.3-tm (dashed line) and the 1.5-tm (solidline) QD lasers is shown in Fig. 5. Layer sequence of the metamorphic-based l.5-trn laser looks very similar to theconventional 1.3-jim QD laser on GaAs. Approximately 2025% of InAs is added to all the layers. The structure isinitialized from a metamorphic InGaAs buffer layer.


>a)

4. EPITAXIAL GROWTH OF METAMORPHIC EPILAYERS

The structures presented were grown by molecular-beam epitaxy (MBE) on GaAs (100) substrates using a Riber 32Pmachine. 2-tm-thick InGa1_As epilayers with different In mole fraction x ranging from 16 to 26% were deposited ontoGaAs at different growth conditions. Deposition temperature, As overpressure, etc., were varied. Linear or stepcompositional gradients were obtained. Also, Si- and Be-doped InAlGaAs epilayers were studied to ensure suitableelectrical characteristics.

The composition, structural quality, and degree of strain relaxation were evaluated by high-resolution x-ray diffraction(HRXRD). Carrier concentration and mobility were measured at 300 K by the Van der Pauw method using a BioRadsetup. Surface morphology and dislocations density were studied by scanning (SEM) and transmission (TEM) electronmicroscopy. Photoluminescence measurements were carried out using laser (W= 500 W cm2, A. = 514 nm) in the77300 K temperature range. A Ge photodiode was used as a signal detector.

As opposed to ideal metamorphic growth, formation of both interface and threading dislocations is typically observed.Threading dislocations are especially dangerous from the viewpoint of possible light-emitting applications because theypropagate through the whole thickness of the epitaxial layer. We found that interface-to-threading dislocations ratiodepends on the growth conditions. Formation of the threading dislocations can be effectively eliminated by carefuloptimization of the structure design and growth regimes. As an example, TEM images of the samples grown at differenttemperatures are presented in Fig. 6. It is seen that that decrease of epitaxial temperature results in domination ofinterface-type dislocations while the threading those are suppressed. Use oflowered temperatures for the layer deposition( 400 C) allows one to confme most of dislocations inside the buffer and avoid their propagation into the upper layers.Surface morphology depends to a certain extent on temperature of buffer deposition. The growth mode switches to theisland type if too low temperatures ( 350 C) are used which is also confirmed by spotty RHEED pattern. Two-steptemperature regime, when the initial buffer is deposited at 400 C and the rest of structure at 500 C, provides smoothlayer surface in combination with filtering of threading dislocations. The dislocation density in the upper layers of about2x108 cm2 was estimated by plan-view TEM images. The degree of strain relaxation is as high as 99.7% as evaluated byHRXRD curves taken near asymmetric (115) GaAs reflexes.

AlAs

AIGaAscladding

AJGaAscladdin

a) a)i, '-a) jLd a)

1.4

1.3

1.2

GaAscap

0.2 0.4 0..x (InAs mole fraction)

1.1

1.0

0.9

InCaAs

0.8

Figure 4. Band gap of quaternary alloy(300 K) as a function oflnAs and AlAs fractions.

0 1 2 3 4 5 6 7Distance, tm

Figure 5. Band gap profile of 1.3-tm (dashed line) and 1.5-tm(solid line) QD laser structures. In the latter case thepseudomorphic growth mode is supposed.


E0

0000V

C/)IJ

1016 iO'7 1018 i09

Conductivity of Be- and Si-doped In(A1Ga1_)iAs metamorphic layers (x2O25%) was studied to make a conclusionconcerning applicability of layers metamorphic for fabricating components of laser structure. We found that p-typedoped layers demonstrate free-hole concentration in a good agreement with that of GaAs:Be regardless the Alcomposition. At the same time, free-electron concentration in n-type doped epilayer decreases with increasing Alsubfraction, y. Room-temperature concentration against Al subfraction, y, is shown in Fig. 7. A significant problem withconductivity was found for the samples with y> 50% (two order of magnitude drop in the electron concentration ascompared to the concentration of Si atoms).

A GaAS

E00

I

Figure 6. Cross-section TEM images of 1n02Ga08As metamorphic layers deposited on GaAs surface at different temperatures. Blackarrows mark some threading dislocations.

io3

102

101

1J

0 20 40 60 80 100

Do

AI/(A1+Ga) ratio, %Figure 7. Dependence of 300K electron concentration in Si-doped In0.2(ALGa1_)o.8As metamorphic epilayers on Alsubfraction.

00

Carrier concentration, cm3Figure 8. Correlation between carrier concentration and specificconductivity in Si-doped GaAs (triangles), Al0 3Ga0 7As(squares), Al08Ga2As (rhombs), and metamorphicIn02Al03Ga5As (solid circles).


Ct

0)

On the other hand, the samples with lower Al content (y S 40%) can be effectively doped to over 1018 cm3 while theelectron mobility is about 800900 cm2V1s'. As a result, the specific conductivity of In0.2(Al,,Ga1_)0.8As:Si (y - 30%)can reach 300 i'cm'. This is much higher than that of Al03Ga2As and corresponds to the highest conductivity level ofAl03Ga7As:Si (see Fig. 8), two most common materials for cladding layers in l.3-im QD lasers.

5. QUANTUM DOTS IN A METAMORPHIC MATRIX

Formation of island array on top of metamorphic InGaAs layer is confirmed by transition of RHEED pattern fromstreaky to spotty upon deposition of approximately 1.8 ML of InAs. TEM micrograph of IriAs QD array formed in ametamorphic In2Ga3As matrix is presented in Fig. 9. Quantum dots are approximately 1520 nm in diameter with thesurface density ofabout loll cm2.

lOOnmFigure 9. Plan-view TEM image oflnAs QD array formed ina metamorphic In02Ga8As matrix.

Ct

LI,C0)C

Wavelength, nmFigure 11. Room-temperature PL spectra from 4-nm-thickIn04GaAs quantum well (QW), 2.7ML InAs quantum-dotarray (QDs), and 2.7ML QD array capped with In0 4Ga,AsQW (QDs in QW) having the same matrix band gap of1.12 eV.

0 1 2 3 4InAs, ML

Figure 10. Dependence of room-temperature PL peak position(solid symbols) and PL intensity (open symbols) on the effectivethickness of InAs forming QD array in a metamorphicIn02Ga8As matrix.

1600

e 15000(I)001U01 1400

1300

300

250

200

150

100C)0

500

1000 1100 1200 1300 1400 1500 1000 1050 1100 1150

Matrix bandgap, meVFigure 12. Dependence of QD emission wavelength (solidcircles) and QD localization energy (open circles) on the bandgap of metamorphic InGa1As matrix. QD array is capped with4-nm-thick In+2Ga.3_As QW.


Dependence of room-temperature PL peak position and PL intensity on the effective thickness of InAs forming QD arrayis shown in Fig. 10. The band gap of a metamorphic matrix was about 1.1 eV. In the QD growth mode (24 ML) PLpeak position is red-shifted with increasing the InAs thickness from 1.33 to 1.37tm indicating the growth of QDs in size.Wavelength of QDs in a metamorphic matrix is approximately 150 nm longer as compared to that of InAs/GaAs QDs forthe same amount of InAs (compare with data of Fig. 1). This is a direct consequence of narrower band gap of the matrixmaterial. Intensity of QD line initially increases (up to -2.7ML of InAs) and then abruptly drops due to plastic strainrelaxation.

Wavelength of QD emission can be shifted beyond 1.4 tm by capping InAs QD array with InGaAs QW. Similar methodwas discussed in Sec. 2 for achieving the 1 .3-trn emission in a GaAs matrix. In the discussed case of metamorphicstructures InAs composition in the capping QW is 2O% higher than that in the metamorphic matrix, QW width is 4 nm.PL spectra of QW, QD array, and QD array capped with QW are compared in Fig. 1 1 for the matrix band gap of 1110meV. For the same matrix band gap this approach results in additional 130-nm shift of QD line to longer wavelengths.QD line can be controllably red shifted up to 1.6 im by varying the matrix composition (matrix band gap), see Fig. 12.Thus, QD structures grown in a metamorphic matrix completely cover the wavelength interval of optical fibercommunication (see Fig. 3).With increasing InAs mole fraction in the matrix (decreasing the matrix band gap) the energy separation between QDline and the matrix band gap slightly decreases (Fig. 12). However, the effective localization energy exceeds 200 meVeven for the QDs emitting at the longest wavelength. This should be sufficient for effective prevention of thermallyactivated carrier escape out of QD states to the matrix at RT.

6. DIODE LASERS BASED ON METAMORPHIC QUANTUM DOTSWe applied metamorphic approach for fabricating long-wavelength lasers on GaAs substrates. InAs mole fractionthroughout the structure is 21% excluding a QD active region. 1.6-tm-thick InAlGaAs claddings doped with Si or Behave Al composition of 35%. A 0.7-tm-thick undoped InGaAs layer is used as a waveguide as well as a matrix for QDformation. From 5 to 15 QD planes separated by 45-nm-thick spacer layers are deposited in the center. Each QD layer isformed by deposition of 2.7 ML of InAs and covered with 4-nm-thick In041Ga59As QW. A Be-doped InGaAs contactlayer terminates the structure.Broad-area lasers with a 100 tm stripe width were fabricated. No facet coatings were deposited. N- and p-type contactswere made using deposition and melting at 450 C of AuGe/NiIAu and AuZn/Ni/Au metallic layers, respectively. Lasercharacteristics were measured inside the 2085 C temperature region using the excitation with 0.2-ts current pulses. Toevaluate internal device parameters, mirror loss was varied by changing the cavity length L. Also, laser structures withfour cleaved facets were evaluated. Such kind of laser cavity emulates the stripe laser of infmite length (V' 0) becausethe mirror loss is negligible.

Threshold current density measured at RT and lasing wavelength taken near the threshold are shown in Fig. 13 asfunctions of the reciprocal cavity length for the stnicture with 10 QD planes. Minimum threshold current density of 800A/cm2 and the longest wavelength of 1 .49 tm are achieved in the resonator with four cleaved facets. Lasing proceeds onthe ground state up to 1-mm-long cavity. This means that the saturated gain on the ground state exceeds 10 cm1. Withvarying the cavity length from 2 to 1 mm the threshold current density increases from 1 .4 to 2 kA/cm2 while thewavelength changes very slightly from 1463 to 1458 nm. This also indicates a sufficient gain on the QD ground state. Inall lasers the lasing peak is shifted towards the longer wavelength with respect to PL peak position at 1.45 im measuredin a sample with etched-off contact layer.

Dependence of the minimum threshold current density (resonators with four cleaved facets) on the number of QD planesin the laser active region is shown in Fig. 14. The lowest threshold current density of 700 A/cm2 was measured in thelaser structure with 5 planes of metamorphic QDs. Increase of the threshold current density to 5.3 kA/cm2 is probablyattributed to formation of dislocations in the active region due to excessive strain.


1490r

1480tj ci

1470

1460

1450

Figure 13. Threshold current density (solid circles) and lasingwavelength (open circles) against reciprocal length of broad-area laser with 10 planes of metamorphic QDs.

Figure 14. Dependence of the minimum threshold currentdensity (resonators with four cleaved facets) in the number ofQD planes in the laser active region.

10 15Drive current, A

Figure 15. Light-current characteristic in pulse regime andlasing spectra (insert) for broad-area metamorphic QD laser.

Figure 16. Temperature dependence of the threshold current(solid circles) and lasing wavelength (open circles).

Example of light-current characteristic of a representative metamorphic QD laser is shown in Fig. 15. The maximumpower in pulse regime exceeds 7 W. The lasing spectra shown in the insert demonstrate the absence of any current-induced shift of the wavelength. Up to the maximum drive current of 23 A quantum dots lase on the ground state withthe wavelength of 1.46 tm. The external differential efficiency is 50%. From the dependence of the external differentialefficiency on cavity length the following internal parameters were extracted: internal efficiency as high as 60% andinternal loss of-3 cm'.

Temperature dependence of the threshold current and lasing wavelength is presented in Fig. 16. Maximum operationtemperature comes to 80 C, the characteristic temperature of the laser threshold, T0, is 61K. Lasing wavelength is

2500 1500

I

2000

1500 . O1000

500

0

I.''io4io3

102I . I . I . I . I

0 2 4 6 8 10

Reciprocal cavity length ilL, cm15 10

Number of QD planes15

8

6

00 5

Wavelenght, am

20 25Ternperature,C


gradually red-shifted with increasing temperature. No temperature-induced transition to the excited-state lasing isobserved.

7. CONCLUSIONS

Formation of self-organized quantum dots in a metamorphic InGa1_As/GaAs (x -2025%) matrix is demonstrated.Special growth regimes are used to confine most of dislocations inside the buffer and avoid their propagation into theupper layers. Metamorphic approach allows one to extend the spectral range of QD structures grown on GaAs substratesup to 1 .58 tm at RI using the sensitivity of QD wavelength to the band gap of surrounding material. QD laser structurebased on metamorphic approach is proposed and realized. Threshold current density and lasing wavelength of themetamorphic QD lasers under investigation corresponds fairly well to the best results published for long-wavelengthlasers on GaAs based on InGaAsSbN.'3 Minimum threshold current density of 800 A/cm2 and operation at 75 C aredemonstrated. Low internal loss and high internal quantum efficiency provides high external differential efficiencyexceeding 50% and high output power over 7W. These structures may have potential in edge- and surface-emitting lasersfor applications in metropolitan area networks and in dense wavelength division multiplexing.

ACKNOWLEDGMENTS

This work was conducted in the framework of joint research project between A. F. loffe Physico-Technical Institute,St. Petersburg, Russia, and NL-Nanosemiconductor-GmbH, Dortmund, Germany.

REFERENCES

1. L. Goldstein, F. Glas, J. Y. Marzin, M. N. Charasse, and G. Le Roux, "Growth by molecular beam epitaxy andcharacterization oflnAs/GaAs strained-layer superlattices", App!. Phys. Lett. 47, 10991101, 1985.

2. D. Leonard, M. Krishnamurthy, L. M. Reaves, S. P. Den Baars, and P. M. Petroff, "Direct formation of quantum-sized dots from uniform coherent islands oflnGaAs on GaAs surfaces", App!. Phys. Lett. 63, 32033205, 1993.

3. A. E. Zhukov, V. M. Ustinov, A. R. Kovsh, A. Yu. Egorov, N. A. Maleev, N. N. Ledentsov, A. F. Tsatsul'nikov,M. V. Maximov, Yu. G. Musilthin, N. A. Bert, P. 5. Kop'ev, D. Bimberg, and Zh. I. Alferov, "Control of theemission wavelength of self-organized quantum dots: main achievements and present status", Semicond. Sd.TedhnoL 14, 575581, 1999.

4. V. M. Ustinov and A. E. Zhukov, "GaAs-based long-wavelength lasers", Semidond. Sdi. Tedhno!. 15, R41R54,2000.

5. Y. Arakawa and H. Sakaki, "Multidimensional quantum well laser and temperature dependence of its thresholdcurrent", App!. Phys. Lett. 40, 939941, 1982.

6. V. M. Ustinov, A. E. Zhukov, A. Yu. Egorov, N. A. Maleev, Quantum Dot Lasers, Oxford University, Oxford, 2003.7. N. N. Ledentsov et a!., unpublished.8. V. M. Ustinov, N. A. Maleev, A. B. Zhukov, A. R. Kovsh, A. Yu. Egorov, A. V. Lunev, B. V. Volovik,

I. L. Krestnikov, Yu. G. Musikhin, N. A. Bert, P. S. Kop'ev, Zh. I. Alferov, N. N. Ledentsov, and D. Bimberg,"InAs/InGaAs quantum dot structures on GaAs substrates emitting at 1.3 tm", App!. Phys. Lett. 74, 28152817,1999.

9. A. E. Zhukov, V. M. Ustinov, A. Yu. Egorov, A. R. Kovsh, A. F. Tsatsul'nikov, M. V. Maximov, N. N. Ledentsov,S. V. Zaitsev, N. Yu. Gordeev, V. I. Kopchatov, Y. M. Shernyakov, P. S. Kop'ev, D. Bimberg, and Zh. I. Alferov,"Injection Lasers Based on InGaAs Quantum Dots in an A1GaAs Matrix", I E!edtron. Mater. 27, 106109, 1998.

10. V. M. Ustinov, E. R. Weber, S. Ruvimov, Z. Liliental-Weber, A. E. Zhukov, A. Yu. Egorov, A. R. Kovsh, A. F.Tsatsul'nikov, and P. 5. Kop'ev, App!. Phys. Lett. 72 (3), 362364, 1998.

11. A. E. Zhukov, A. P. Vasil'ev, A. R. Kovsh, S. S. Mikhrin, E. S. Semenova, A. Yu. Egorov, V. A. Odnoblyudov,N. A. Maleev, B. V. Nikitina, N. V. Kryzhanovskaya, A. G. Gladyshev, Yu. M. Shernyakov, M. V. Maximov,N. N. Ledentsov, V. M. Ustinov, and Zh. I. Alferov, "Lasing at 1.5 im in quantum dot structures on GaAssubstrates", Semic'ondudtors 37, 14611464, 2003.


12. Sh.-I. Gozu, K. Tsuboki, M. Hayashi, Ch. Hong, S. Yamada, "Very high electron mobilities at low temperatures inInGaiAs/InA1iAs HEMTs grown lattice-mismatched on GaAs substrates", J. Cryst. Growth 201202, 749752,1999.

13. W. Ha, V. Gambin, S. Bank, M. Wistey, H. Yuen, S. Kim, and J. S. Harris., "Long-Wavelength GaInNAs(Sb) Laserson GaAs", IEEE J. Quantum Electron. 38, 12601267, 2002.

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