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  • 1. Baskar, K.
    et al.
    Sundgren, P.
    Douheret, O.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Surface morphology and localised states of GaInNAs single quantum wells grown by MOVPE2003In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 248, p. 431-436Article in journal (Refereed)
    Abstract [en]

    GaInNAs/GaAs single quantum wells (QWs) have been grown by metalorganic vapour phase epitaxy (MOVPE). The surface morphology has been studied by atomic force microscopy (AFM). The density of pits observed on the surface of QW structures was found to depend on the growth temperature and dimethylhydrazine (DMHy) flow. Cross-sectional AFM image showed the presence of defects at the interface of GaInNAs/GaAs. The low temperature photoluminescence characteristics of the QWs as a function of growth temperature. DMHy flow and density of surface pits have been discussed. The origin of pit formation is addressed based on the pyrolysis products present during the growth of QWs. The results suggest that higher growth temperature maybe desirable to obtain good quality GaInNAs QWS.

  • 2. Bowallius, O.
    et al.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Nordell, N.
    Landgren, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, S.
    Scanning capacitance microscopy investigations of SiC structures2001In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 4, no 03-jan, p. 209-211Article in journal (Refereed)
    Abstract [en]

    We have applied scanning capacitance microscopy (SCM) to investigate SIC structures grown by vapour-phase epitaxy. The SCM technique is evaluated using n- and p-type doping staircase structures with doping concentrations ranging from 10(16) to 10(20) cm(-3). The n- and p-type doping was obtained by doping SiC with nitrogen and aluminium, respectively. The sample cross-sections for SCM were obtained by simple cleaving. For doping levels above 10(17) cm(-3) the SCM data are consistent with doping data obtained independently from secondary ion mass spectroscopy (SIMS). Treating the samples with diluted hydrofluoric acid significantly improves the SCM signal for the low-doped regions. The SCM technique has been used to investigate doping redistribution in patterned regrowth of n- and p-type SIC around dry-etched mesas. In both cases, contrast variations were seen close to the mesa walls, indicative of doping variations; lower and higher incorporation for p- and n-type, respectively. The observations are shown to be consistent with the expected trends in dopant incorporation in the SiC material.

  • 3.
    Campi, Roberta
    et al.
    Turin Technology Center.
    Berggren, Jesper
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Buccieri, Aurelio
    Turin Technology Center.
    Gotta, Paola
    Turin Technology Center.
    Landgren, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sarocchi, Davide
    Turin Technology Center.
    Valenti, P.
    Turin Technology Center.
    Lateral confinement optimisation of 1300 nm InGaAlAsP/InGaAsP Fabry-Perot lasers2003In: EWMOVPEX: 10th European Workshop on Metalorganic Vapour Phase Epitaxy, 2003Conference paper (Refereed)
  • 4.
    Campi, Roberta
    et al.
    KTH, Superseded Departments, Electronics.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Physics.
    Landgren, Gunnar
    KTH, Superseded Departments, Electronics.
    Studies on the carrier transport in InGaAlAdP/InGaAsP quantum well structures emitting at 1.3 μm2000In: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2000, p. 141-Conference paper (Refereed)
    Abstract [en]

    A novel approach to improve high temperature performance in the IngaAsP lasers was examined by adding aluminum to the barrier,which allows to increase conduction band offset. To find optimal heterostructure parameters, different barrier material compositions were examined in structures with InGaAsP compressively strained wells and tensile strained InGaAlAsP barriers. The MQW structures were fabricated by low pressure MOVPE.

  • 5.
    Campi, Roberta
    et al.
    KTH, Superseded Departments, Electronics.
    Patel, Amit
    KTH, Superseded Departments, Electronics.
    Landgren, Gunnar
    KTH, Superseded Departments, Electronics.
    MOVPE growth of strained 1300 nm InGaAlAsP/ InGaAsP quantum well structures2000In: 12th International Conference on Indium Phosphide and Related Materials, 2000, p. 380-383Conference paper (Refereed)
    Abstract [en]

    In this work we propose novel 1.3 μm InGaAlAsP/InGaAsP MQW laser structures designed for high-temperature operation. The effects of aluminum on the band offsets and carrier confinement in MQW structures have been investigated. Epitaxial structures exhibited very high photoluminescence (PL) and sharp satellites in high-resolution x-ray diffraction. The carrier transport issues were further investigated using femtosecond time-resolved PL. Broad area lasers exhibited values of threshold current density of 261 A/cm-2 per quantum well and a slope efficiency of 0.25 W/A. The observed T0 values of 69 K for pure InGaAsP barriers increased to about 95 K for an Al content of about 12.5%, in accordance with expectations.

  • 6. Grahn, J. V.
    et al.
    Fosshaug, H.
    Jargelius, M.
    Jonsson, P.
    Linder, M.
    Malm, B. Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mohadjeri, B.
    Pejnefors, J.
    Radamson, Henry H.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sanden, M.
    Wang, Yong-Bin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Landgren, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A low-complexity 62-GHz f(T) SiGe heterojunction bipolar transistor process using differential epitaxy and in situ phosphorus-doped poly-Si emitter at very low thermal budget2000In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 44, no 3, p. 549-554Article in journal (Refereed)
    Abstract [en]

    A low-complexity SiGe heterojunction bipolar transistor process based on differential epitaxy and in situ phosphorus doped polysilicon emitter technology is described. Silane-based chemical vapor deposition at reduced pressure was used for low-temperature SiGe epitaxy. Following SiGe epitaxy, the process temperature budget was kept very low with 900 degrees C for 10 s as the highest temperature step. A very high current gain of almost 2000 and cut off frequency of 62 GHz were achieved for a uniform 12% Ge profile. The breakdown voltage BVCEO and forward Early voltage were equal to 2.9 and 6.5 V, respectively.

  • 7. Keiper, D.
    et al.
    Velling, P.
    Prost, W.
    Agethen, M.
    Tegude, F. J.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Metalorganic vapour phase epitaxy growth of InP-based heterojunction bipolar transistors with carbon doped InGaAs base using tertiarybutylarsine and tertiarybutylphosphine in N-2 ambient2000In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 39, no 11, p. 6162-6165Article in journal (Refereed)
    Abstract [en]

    A process for growth of heterostructure bipolar transistors (HBT) using tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) in N-2 ambient is realised, which is compatible with a high temperature overgrowth, thus suitable for the vertical integration Of a laser structure on top of an HBT. A high growth temperature for the C-InGaAs base is favourable, to ensure no: degradation during subsequent growth. Increasing the growth temperature after the base from 500 degreesC to 680 degreesC within the emitter layer instead of at the base-emitter interface was found to improve the ideality factors, the de gain and the turn-on voltage.

  • 8. Keiper, D.
    et al.
    Westphalen, R.
    Landgren, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Growth of quaternary InP-based materials by LP-MOVPE using TBA and TBP in N-2 ambient2000In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 29, no 12, p. 1398-1401Article in journal (Refereed)
    Abstract [en]

    We have investigated the growth of quaternary In1-xGaxAsyP1-y/InP materials using TEA and TBP in a N-2 ambient. This process improves significantly the uniformity of In1-xGaxAs/InP QWs whereas it does not improve the quaternary Q(1.3)/InP uniformity compared to the conventional process utilizing AsH3 and PH3 in H-2. The effect on the x and y uniformity for different combinations of the group-V precursors TBA, TBP, PH3, and AsH3 with the carrier gases H-2 and N-2 is evaluated. Advantages with the TBA/TBP/N-2 process are discussed.

  • 9.
    Kjebon, Olle
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hammarlund, B.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lindgren, S.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rask, M
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ojala, P.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Landgren, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Broberg, B.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    1.55 μm buried heterostructure laser via regrowth of semi-insulating InP:Fe around vertical mesas fabricated by reactive ion etching using methane and hydrogen1991In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 59, no 3, p. 235-255Article in journal (Refereed)
    Abstract [en]

    A GaInAsP/InP Fabry-Perot-type buried-heterostructure quantum well laser operating at 1.55 μm has been realized utilizing iron-doped semi-insulating InP around vertical mesas fabricated by reactive ion etching using methane and hydrogen. A maximum cw output power of 19 mW has been achieved on as-cleaved chips of 300 μm length with a quantum efficiency of 21% per facet. Threshold currents lie between 20 and 25 mA. As low as 2 Ω series resistance has been measured despite an ohmic contact area not exceeding that of the 2-μm-wide mesa. A 3 dB bandwidth of 7.5 GHz at 12 mW output power is obtained from the small-signal frequency modulation measurements.

  • 10.
    Lourdudoss, Sebastian
    et al.
    KTH, Superseded Departments, Electronics.
    Rodríguez Messmer, E.
    KTH, Superseded Departments, Electronics.
    Kjebon, Olle
    KTH, Superseded Departments, Electronics.
    Landgren, Gunnar
    KTH, Superseded Departments, Electronics.
    Temporally resolved selective regrowth of InP around [110] and [110] mesas1996In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 25, no 3, p. 389-394Article in journal (Refereed)
    Abstract [en]

    Temporally resolved selective regrowth of InP around reactive ion etched [110] and [110] directional mesas is studied by hydride vapor phase epitaxy at the growth temperatures of 600, 650, 685, and 700°C. The regrowth profiles are strikingly different depending upon the mesa orientation. The results are interpreted by invoking the difference in the bonding configurations of these mesas as well as the growth facility in a direction leading to the largest reduction of dangling bonds under the growth conditions. Various emerging planes during regrowth are identified and are {hhl} planes with initial values of l/h ≤ 3 but ≥ 3 as the planarization is approached. Initial lateral growth defined as the growth away from the mesa at half of its height in the very first minute is a decreasing function of temperature when plotted as Arrhenius curves. Such a behavior is attributed to the exothermicity of the reaction and to an enhanced pyrolysis of PH3 to P2. The lateral growth rate is much larger than that on the planar substrate. This should be taken into account when regrowth of a doped layer (e.g. InP:Fe or InP:Zn) is carried out to fabricate a buried heterostructure device since the dopant concentration can be very much lower than the one optimized on the planar substrates.

  • 11. Menon, C.
    et al.
    Bentzen, A.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Radamson, H. H.
    Defect density in non-selective and selective Si/SiGe structures2002In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 237, p. 259-263Article in journal (Refereed)
    Abstract [en]

    The epitaxial quality of Si (non-selective or selective epitaxy)/SiGe (non-selective or selective epitaxy) structures applying Si2H2Cl2 or SiH4 as the Si source has been studied. High-resolution reciprocal lattice mapping and X-ray reflectivity measurements have been used to characterise the epitaxial quality and the interfacial defects, respectively. The surface morphology of the structures was studied by atomic force microscopy. It is shown that the generation of defects in non-selective SiGe layers is strongly dependent oil the thickness of the buffer layer. Moreover, the selective growth of a Si buffer layer requires a growth temperature above 770degreesC in order to obtain a smooth layer surface, which is beneficial for the succeeding growth of the SiGe layer. The surface can also be smoothed by an annealing treatment at 900degreesC for 40 s. This annealing step is crucial to remove the interfacial defects in the case of Si/SiGe structures grown with different Si sources.

  • 12. Radamson, H. H.
    et al.
    Bentzen, A.
    Menon, C.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Observed critical thickness in selectively and non-selectively grown Si1-xGex layers on patterned substrates2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T101, p. 42-44Article in journal (Refereed)
    Abstract [en]

    Relaxation of SiGe layers grown selectively or non-selectively on oxide-patterned substrates using reduced pressure chemical vapor deposition was investigated. The influences of the buffer layer, the polycrystalline layer on the oxide and the opening size on the critical thickness for relaxation of SiGe layers have been studied in detail. High resolution reciprocal lattice mapping, atomic force microscopy and Normanski optical microscope have been used as the main characterization tools.

  • 13. Radamson, H. H.
    et al.
    Mohadjeri, B.
    Menon, C.
    Bentzen, A.
    Grahn, J.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Growth of high frequency SiGe heterojunction bipolar transistors structures2002In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T101, p. 45-48Article in journal (Refereed)
    Abstract [en]

    The growth of heterojuntion bipolar transistor structures using chemical vapor deposition has been investigated. Generation of defects in selectively or nonselectively grown collector layers using arsenic as the dopant has been studied. Minimizing the defect density in SiGe base layers by optimizing the growth rate has also been investigated in detail. High resolution reciprocal lattice mapping, atomic force microscopy and secondary ion mass spectrometry have been used as the main characterization tools.

  • 14. Suresh, S.
    et al.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Landgren, Gunnar
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Baskar, K.
    Studies on the effect of ammonia flow rate induced defects in gallium nitride grown by MOCVD2010In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 312, no 21, p. 3151-3155Article in journal (Refereed)
    Abstract [en]

    Gallium nitride (GaN) epitaxial layers were grown with different V/III ratios by varying the ammonia (NH3) flow rate, keeping the flow rate of the other precursor, trimethylgallium (TMG), constant, in an MOCVD system. X-ray rocking curve widths of a (1 0 2) reflection increase with an increase in V/III ratio while the (0 0 2) rocking curve widths decrease. The dislocation density was found to increase with an increase in ammonia flow rate, as determined by hot-wet chemical etching and atomic force microscopy. 77K photoluminescence studies show near band emission at 3.49 eV and yellow luminescence peaking at 2.2 eV. The yellow luminescence (YL) intensity decreases with an increase in V/III ratio. Positron annihilation spectroscopy studies show that the concentration of Ga-like vacancies increases with an increase in ammonia flow rate. This study confirms that the yellow luminescence in the GaN arises due to deep levels formed by gallium vacancies decorated with oxygen atoms.

  • 15. Vukusic, J.
    et al.
    Bengtsson, J.
    Ghisoni, M.
    Larsson, A.
    Carlstrom, C. F.
    Landgren, Gunnar.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fabrication and characterization of diffractive optical elements in InP for monolithic integration with surface-emitting components2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 3, p. 398-401Article in journal (Refereed)
    Abstract [en]

    We report on the fabrication and subsequent characterization of binary diffractive optical elements (DOE's) in InP for operation at 1.3 mu m. Fresnel lenses of different focal, lengths and a DOE that splits and focuses an incident beam into a 1 x 4 array of spots (optical fan-out) were fabricated. We realized the surface reliefs by patterning resist, using electron-beam lithography and etching with a chemically assisted ion beam, which produced well-defined patterns with smooth sidewalls and little if no surface roughness. The measured efficiency for the lenses was 36%. For the fan-out element the efficiency and the uniformity error were 26% and 30%, respectively. Spot sizes small as 16 mu m were measured.

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