Dr Konstanze Hild
Research Fellow
Qualifications: Dipl. Phys. (Dortmund) PhD (Surrey)
Email: k.hild@surrey.ac.uk
Phone: Work: 01483 68 9403
Room no: 08 ATI 02
Further information
Biography
1994-2000 Universität Dortmund. Working on the spectroscopy of single excitonic states in II-VI semiconductor structures for the Diplom obtained in January 2000.
2000-2003 University of Surrey. The PhD work (Surrey 2003) concerned the spectroscopy (photomodulated reflectance) and device measurements of Resonant Cavity LEDs emitting at 650nm.
2005-2008 Research Assistant (University of Surrey) working on GaAsSb based lasers for emission at 1.3 microns.
Since January 2011 working as a Research Fellow on the optical characterisation of Bismuth containing semiconductors.
Publications
Journal articles
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(2013) 'The influence of growth conditions on carrier recombination mechanisms in 1.3 μm GaAsSb/GaAs quantum well lasers'. Applied Physics Letters, 102 (4)doi: 10.1063/1.4789859
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(2012) 'Temperature and Bi-concentration dependence of the bandgap and spin-orbit splitting in InGaBiAs/InP semiconductors for mid-infrared applications'. Applied Physics Letters, 101 (22)doi: 10.1063/1.4768532Full text is available at: http://epubs.surrey.ac.uk/745673/
Abstract
Replacing small amounts of As with Bi in InGaBiAs/InP induces large decreases and increases in the bandgap, E, and spin-orbit splitting, Δ, respectively. The possibility of achieving Δ > E and a reduced temperature (T) dependence for E are significant for suppressing recombination losses and improving performance in mid-infrared photonic devices. We measure E (x, T) and Δ (x, T) in InGa BiAs/InP samples for 0 x 0.039 by various complementary optical spectroscopic techniques. While we find no clear evidence of a decreased dE/dT (≈0.34 ± 0.06 meV/K in all samples) we find Δ > E for x > 3.3-4.3. The predictions of a valence band anti-crossing model agree well with the measurements. © 2012 American Institute of Physics.
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(2012) 'Cavity mode gain alignment in GaAsSb-based near-infrared vertical cavity lasers studied by spectroscopy and device measurements'. Journal of Applied Physics, 112 (3)doi: 10.1063/1.4744985Full text is available at: http://epubs.surrey.ac.uk/728516/
Abstract
We present a combination of spectroscopy and device measurements on GaAsSb/GaAs vertical-cavity surface-emitting laser (VCSEL) structures to determine the temperature at which the wavelength of the VCSEL cavity mode (CM) aligns with that of the quantum well (QW) ground-state transition (GST), and therefore the gain peak. We find that, despite the achievement of room temperature (RT) continuous wave lasing in VCSEL devices, the QW transition and the CM are actually slightly misaligned at this temperature; room temperature electroluminescence measurements from a cleaved edge of the VCSEL wafer indicate that the 300 K QW GST energy is at 0.975 ± 0.005 eV, while the CM measured in the VCSEL surface reflectivity spectra is at 0.9805 ± 0.0002 eV. When the wafer sample is cooled, the CM and QW GST can be brought into alignment at 270 ± 10 K, as confirmed by temperature-dependent electro-modulated reflectance (ER) and edge-electroluminescence spectroscopic studies. This alignment temperature is further confirmed by comparing the temperature dependence of the emission energy of a fabricated VCSEL device with that of an edge-emitting laser structure with a nominally identical active region. The study suggests that for further device improvement, the room temperature CM and QW GST energies should be more closely matched and both designed to a smaller energy of about 0.95 eV, somewhat closer to the 1.31 μm target. The study amply demonstrates the usefulness of non-destructive ER characterisation techniques in VCSEL manufacturing with GaAsSb-based QWs. © 2012 American Institute of Physics.
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(2012) 'The electronic band structure of GaBiAs/GaAs layers: Influence of strain and band anti-crossing'. AMER INST PHYSICS JOURNAL OF APPLIED PHYSICS, 111 (11) Article number ARTN 113108 doi: 10.1063/1.4728028Full text is available at: http://epubs.surrey.ac.uk/728515/
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(2012) 'Recombination mechanisms and band alignment of GaAs1-xBix/GaAs light emitting diodes'. APPLIED PHYSICS LETTERS, 100 (5) Article number ARTN 051105 doi: 10.1063/1.3681139Full text is available at: http://epubs.surrey.ac.uk/531960/
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(2011) 'Influence of de-tuning and non-radiative recombination on the temperature dependence of 1.3 mu m GaAsSb/GaAs vertical cavity surface emitting lasers'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 99 (7) Article number ARTN 071110 doi: 10.1063/1.3625938Full text is available at: http://epubs.surrey.ac.uk/7832/
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(2006) 'Carrier recombination in 1.3 mu m GaAsSb/GaAs quantum well lasers'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 89 (17) Article number ARTN 173509 doi: 10.1063/1.2369649Full text is available at: http://epubs.surrey.ac.uk/104830/
- . (2005) 'On the thermal stability of 1.3 mu m GaAsSb/GaAs-based lasers'. IEEE 2005 IEEE LEOS Annual Meeting Conference Proceedings (LEOS), Sydney, AUSTRALIA: , pp. 330-331.
Conference papers
- . (2012) 'InGaBiAs/InP semiconductors for mid-infrared applications: Dependence of bandgap and spin-orbit splitting on temperature and bismuth content'. ICP 2012 - 3rd International Conference on Photonics 2012, Proceedings, , pp. 154-158.
- . (2011) 'The Potential Role of Bismide Alloys in Future Photonic Devices'. IEEE 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, Stockholm, Sweden: 13th ICTON
- . (2010) 'Role of growth temperature on the physical characteristics of GaAsSb/GaAs QW lasers'. IEEE 23rd Annual Meeting of the IEEE Photonics Society, Denver, USA: Photonics 2010, pp. 59-60.
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(2010) 'Influence of device structures on carrier recombination in GaAsSb/GaAs QW lasers'. Proceedings of Photonics Global Conference, Orchard, Singapore: PGC 2010Full text is available at: http://epubs.surrey.ac.uk/733523/
Abstract
We investigate the temperature and pressure dependence of carrier recombination processes occurring in various GaAsSb/GaAs QW laser structures grown under similar growth conditions. Thermally activated carrier leakage via defects is found to be very sensitive to the strain induced interface imperfections. Nonradiative recombination is found to be sensitive to the number of QWs. A strain compensated MQW structure leads to a reduced contribution of non-radiative recombination to the threshold current density (Jth) and a high characteristic temperature (T0) of 73K at room temperature.
- . (2008) 'Thermal characteristics of 1.3 mu m GaAsSb/GaAs-based Edge- and Surface-emitting Lasers'. IEEE 2008 IEEE 21ST INTERNATIONAL SEMICONDUCTOR LASER CONFERENCE, Sorrento, ITALY: IEEE 21st International Semiconductor Laser Conference, pp. 83-84.
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(2007) 'Band alignment and carrier recombination in GaAsSb/GaAs quantum wells'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 1431-1432.Full text is available at: http://epubs.surrey.ac.uk/733534/
- . (2007) 'Temperature and pressure dependence of carrier recombination processes in GaAsSb/GaAs quantum well lasers'. WILEY-V C H VERLAG GMBH PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Barcelona, SPAIN: 12th International Conference on High Pressure Semiconductor Physics (HPSP-12) 244 (1), pp. 197-202.
- . (2006) 'Analysis of reflectance and modulation spectroscopic lineshapes in optoelectronic device structures'. ELSEVIER SCIENCE BV APPLIED SURFACE SCIENCE, Strasbourg, FRANCE: Symposium P of the Spring Meeting of the European-Materials-Research-Society entitled Curent Trends in Optical and X-ray Meterology of Advanced Materials for Nanoscale Devices 253 (1), pp. 70-79.
