Inst. Festkörperphysik

271 Items

Recent Submissions
Group III-nitride based UVC LEDs and lasers with transparent AlGaN:Mg layers and tunnel junctions grown by MOVPE

Kuhn, Christian (2020)

In this work, AlGaN-based light-emitting diodes (LEDs) and lasers with emission wavelengths in the deep ultraviolet (UVC) spectral range are produced, analyzed, and optimized. Here, the focus is on the UV transparency of the structures, enabling high light extraction efficiency for UVC LEDs and being a necessary condition for UVC laser diodes, however at the same time challenging due to low ele...

Heterostructure design and epitaxial growth of AlGaN-based light emitting diodes emitting in the UVC wavelength range

Susilo, Norman (2020)

AlGaN-based ultraviolet-C (UVC) light emitting diodes (LEDs) can be applied to a wide range of applications. However, the efficiency of UVC-LEDs is still relatively modest, which provides the focus of this thesis: The development of efficient UVC-LEDs with emission wavelengths near 265 nm. This thesis presents a systematic study of the influence of the heterostructure design and the layer prope...

Twofold gain enhancement by elongation of QDs in polarization preserving QD-SOAs

Greif, Ludwig Albrecht Thorsten ; Mittelstädt, Alexander ; Jagsch, Stefan Thomas ; Schliwa, Andrei (2019-06-06)

The impact of quantum dot (QD) elongation on key parameters of QD-based semiconductor optical amplifiers (SOAs) is investigated using a combination of 8-band k·p-theory including strain and piezoelectricity up to second order and a rate equation model describing the population of QD ground, excited and wetting layer states. By considering columnar QDs of selected aspect ratios, we show that chi...

Tuning the Emission Directionality of Stacked Quantum Dots

Greif, Ludwig Albrecht Thorsten ; Jagsch, Stefan Thomas ; Wagner, Markus R. ; Schliwa, Andrei (2018-11-02)

The emission directionality of stacks of coupled quantum dots (QDs) is investigated within the framework of 8-band k·p-theory including strain and strain-induced piezoelectricity up to second order. Using an artificial cuboidal QD, we show that the degree of radiation anisotropy can be tuned from −33% to nearly +60% via the structure’s vertical aspect ratio. We then demonstrate that these findi...

Towards a deterministic cavity-integrated III-nitride single-photon source with two-photon resonant control

Jagsch, Stefan Thomas (2020)

Wide band gap III-nitride semiconductors already form the basis of today's industrial-scale diode lighting technology. In this two-part thesis, we explore their potential for cavity-enhanced single-photon applications and high-beta nanolasers at elevated temperatures. The overarching topic is the development of a fully deterministic single-photon source with ground-state resonant two-photon con...

A consistent assignment of Raman modes in individual, single-walled carbon nanotubes

Vierck, Asmus Marx Hinrich (2020)

In the present thesis, a thorough analysis of the exceptional phononic and optoelectronic properties of individual, single-walled carbon nanotubes is established by the use of Raman spectroscopy. While there have been a multitude of Raman studies on carbon nanotubes within the past decades, most of them examined an unordered mixture of tubes - an "ensemble". To gain conclusive results, such mea...

Thin-film flip-chip UVB LEDs realized by electrochemical etching

Bergmann, Michael A. ; Enslin, Johannes ; Hjort, Filip ; Wernicke, Tim ; Kneissl, Michael ; Haglund, Åsa (2020-03-24)

We demonstrate a thin-film flip-chip (TFFC) light-emitting diode (LED) emitting in the ultraviolet B (UVB) at 311 nm, where substrate removal has been achieved by electrochemical etching of a sacrificial Al0.37Ga0.63N layer. The electroluminescence spectrum of the TFFC LED corresponds well to the as-grown LED structure, showing no sign of degradation of structural and optical properties by elec...

Semiconductor nanostructures for flying q-bits and green photonics

Bimberg, Dieter (2018)

Breakthroughs in nanomaterials and nanoscience enable the development of novel photonic devices and systems ranging from the automotive sector, quantum cryptography to metropolitan area and access networks. Geometrical architecture presents a design parameter of device properties. Self-organization at surfaces in strained heterostructures drives the formation of quantum dots (QDs). Embedding QD...

GaAs-based subwavelength grating on an AlOx layer for a vertical-cavity surface-emitting laser

Liu, Anjin ; Yang, Bo ; Wolf, Philip ; Zhang, Jing ; Bimberg, Dieter (2020)

A GaAs-based subwavelength grating on a thick (∼3/4*λ at 1300 nm) AlOx layer is designed, fabricated, and characterized. The AlOx layer as a low-index medium is oxidized from a 640-nm Al0.9Ga0.1As layer. The layer contraction of the Al0.9Ga0.1As layer after wet oxidation to AlOx is 4.9%. We fabricated GaAs-based subwavelength gratings on the AlOx layer showing a high reflectivity of 90% in the ...

Multimode optical feedback dynamics in InAs/GaAs quantum dot lasers emitting exclusively on ground or excited states: transition from short- to long-delay regimes

Huang, Heming ; Lin, Lyu-Chih ; Chen, Chih-Ying ; Arsenijević, Dejan ; Bimberg, Dieter ; Lin, Fan-Yi ; Grillot, Frédéric (2018)

The optical feedback dynamics of two multimode InAs/GaAs quantum dot lasers emitting exclusively on sole ground or excited lasing states is investigated. The transition from long- to short-delay regimes is analyzed, while the boundaries associated to the birth of periodic and chaotic oscillations are unveiled to be a function of the external cavity length. The results show that depending on the...

Fabrication and characterization of integrable GaAs-based high-contrast grating reflector and Fabry-Pérot filter array with GaInP sacrificial layer

Liu, Anjin ; Wolf, Philip ; Schulze, Jan-Hindrik ; Bimberg, Dieter (2016)

Integrable GaAs-based high-contrast gratings (HCGs) are fabricated and characterized, targeting applications in high-speed vertical-cavity surface-emitting lasers (VCSELs). A Ga 0.51 In 0.49 P sacrificial layer beneath the GaAs layer is employed to create a low index surrounding HCG strips by selective etching. Experimental results show that the finite-size HCG has a reflectivity of 93% from 12...

Beam quality improvement of high-power semiconductor lasers using laterally inhomogeneous waveguides

Miah, Mohammad Jarez ; Strohmaier, S. ; Urban, G. ; Bimberg, Dieter (2018)

High-brightness vertical broad-area edge-emitting (HiBBEE) semiconductor lasers in the 1060 nm wavelength range with excellent beam quality in both lateral and vertical directions are presented. An approach to modify the thresholds of the transverse lateral modes of ridge-waveguide (RW) lasers is investigated. It has been experimentally shown that inhomogeneities in both sides of the ridges inc...

Thermal analysis of high-bandwidth and energy-efficient 980 nm VCSELs with optimized quantum well gain peak-to-cavity resonance wavelength offset

Li, Hui ; Wolf, Philip ; Jia, Xiaowei ; Lott, James A. ; Bimberg, Dieter (2017)

The static and dynamic performance of vertical-cavity surface-emitting lasers (VCSELs) used as light-sources for optical interconnects is highly influenced by temperature. We study the effect of temperature on the performance of high-speed energy-efficient 980 nm VCSELs with a peak wavelength of the quantum well offset to the wavelength of the fundamental longitudinal device cavity mode so that...

Fabrication and room temperature operation of semiconductor nano-ring lasers using a general applicable membrane transfer method

Fan, Fan ; Yu, Yueyang ; Amiri, Seyed Ebrahim Hashemi ; Quandt, David ; Bimberg, Dieter ; Ning, C. Z. (2017)

Semiconductor nanolasers are potentially important for many applications. Their design and fabrication are still in the early stage of research and face many challenges. In this paper, we demonstrate a generally applicable membrane transfer method to release and transfer a strain-balanced InGaAs quantum-well nanomembrane of 260 nm in thickness onto various substrates with a high yield. As an in...

Strong amplitude-phase coupling in submonolayer quantum dots

Herzog, Bastian ; Lingnau, Benjamin ; Kolarczik, Mirco ; Kaptan, Yücel ; Bimberg, Dieter ; Maaßdorf, André ; Pohl, Udo W. ; Rosales, Ricardo ; Schulze, Jan-Hindrik ; Strittmatter, André ; Weyers, Markus ; Woggon, Ulrike ; Lüdge, Kathy ; Owschimikow, Nina (2016)

Submonolayer quantum dots promise to combine the beneficial features of zero- and two-dimensional carrier confinement. To explore their potential with respect to all-optical signal processing, we investigate the amplitude-phase coupling (α-parameter) in semiconductor optical amplifiers based on InAs/GaAs submonolayer quantum dots in ultrafast pump-probe experiments. Lateral coupling provides an...

Comparison of dynamic properties of InP/InAs quantum-dot and quantum-dash lasers

Sadeev, Tagir ; Arsenijević, Dejan ; Bimberg, D. (2016)

The dynamic properties of MOVPE grown InP/InAs quantum-dot and quantum-dash lasers, showing identical structural design, emitting in the C-band are investigated and compared to each other. Based on the small-signal measurements, we show the impact of the density of states function on the cut-off frequency, being larger for quantum dots at low currents, and reaching similar values for quantum da...

Growth and structure of In0.5Ga0.5Sb quantum dots on GaP(001)

Sala, Elisa M. ; Stracke, G. ; Selve, S. ; Niermann, T. ; Lehmann, M. ; Schlichting, S. ; Nippert, Felix ; Callsen, G. ; Strittmatter, André ; Bimberg, Dieter (2016)

Stranski-Krastanov (SK) growth of In0.5Ga0.5Sb quantum dots (QDs) on GaP(001) by metalorganic vapor phase epitaxy is demonstrated. A thin GaAs interlayer prior to QD deposition enables QD nucleation. The impact of a short Sb-flush before supplying InGaSb is investigated. QD growth gets partially suppressed for GaAs interlayer thicknesses below 6 monolayers. QD densities vary from 5 × 109 to 2 ×...

Highly efficient non-degenerate four-wave mixing under dual-mode injection in InP/InAs quantum-dash and quantum-dot lasers at 1.55 μm

Sadeev, Tagir ; Huang, Heming ; Arsenijević, Dejan ; Schires, Kevin ; Grillot, F. ; Bimberg, Dieter (2015)

This work reports on non-degenerate four-wave mixing under dual-mode injection in metalorganic vapor phase epitaxy grown InP/InAs quantum-dash and quantum dot Fabry-Perot laser operating at 1550 nm. High values of normalized conversion efficiency of −18.6 dB, optical signal-to-noise ratio of 37 dB, and third order optical susceptibility normalized to material gain χ(3)/g0 of ∼4 × 10−19 m3/V3 ar...

25 Gbit/s differential phase-shift-keying signal generation using directly modulated quantum-dot semiconductor optical amplifiers

Zeghuzi, A. ; Schmeckebier, H. ; Stubenrauch, M. ; Meuer, C. ; Schubert, C. ; Bunge, C.-A. ; Bimberg, Dieter (2015)

Error-free generation of 25-Gbit/s differential phase-shift keying (DPSK) signals via direct modulation of InAs quantum-dot (QD) based semiconductor optical amplifiers (SOAs) is experimentally demonstrated with an input power level of −5 dBm. The QD SOAs emit in the 1.3-μm wavelength range and provide a small-signal fiber-to-fiber gain of 8 dB. Furthermore, error-free DPSK modulation is achieve...

230 s room-temperature storage time and 1.14 eV hole localization energy in In0.5Ga0.5As quantum dots on a GaAs interlayer in GaP with an AlP barrier

Bonato, Leo ; Sala, Elisa M. ; Stracke, Gernot ; Nowozin, Tobias ; Strittmatter, André ; Ajour, Mohammed Nasser ; Daqrouq, Khaled ; Bimberg, Dieter (2015)

A GaP n+p-diode containing In0.5Ga0.5As quantum dots (QDs) and an AlP barrier is characterized electrically, together with two reference samples: a simple n+p-diode and an n+p-diode with AlP barrier. Localization energy, capture cross-section, and storage time for holes in the QDs are determined using deep-level transient spectroscopy. The localization energy is 1.14(±0.04) eV, yielding a stora...