Waltereit, P., Müller, S., Bellmann, K., Buchheim, C., Goldhahn, R., Köhler, K., ...
We systematically investigate Al(0.22)Ga(0.78)N/GaN high electron mobility transistors with GaN cap layer thicknesses of 0, 1, and 3 nm. All samples have electron mobilities around 1700 cm2/Vs and...
Knübel, A., Aidam, R., Cimalla, V., Kirste, L., Baeumler, M., ...
We report on the PAMBE-growth of high-quality InN layers with In polarity and on the influence of growth parameters such as Indium-to-nitrogen flux ratio as well as substrate temperature on the...
Spatial variations of carrier and defect concentration in VGF GaAs:Si (2008)
Baeumler, M., Boerner, F., Kretzer, U., Scheffer-Czygan, M., Bünger, T., Wagner, J.
Wafers cut from Si-doped vertical gradient freeze (VGF) GaAs crystals with silicon concentration varying from 1.5 to 3.4 x 10(18) cm(-3) have been investigated by low temperature photoluminescence...
Kunzer, M., Baeumler, M., Köhler, K., Kaufmann, U., Wagner, J.
A series of (AlGaIn)N LEDs covering the 377 to 428 nm wavelength interval has been analyzed by pulsed electro- and temperature dependent photo-luminescence with respect to the carrier density...
Baeumler, M., Kunzer, M., Schmidt, R., Liu, S., Pletschen, W., Schlotter, P., ...
UV-to-violet emitting (AlGaln)N LEDs have been investigated with respect to the temperature-dependence of the output power characteristics and non-thermal rollover of the quantum efficiency at higher...
Müller, S., Köhler, K., Kiefer, R., Quay, R., Baeumler, M., Kirste, L.
Heterostructures of GaN/AlGaN for power applications are grown by metal organic vapor phase epitaxy in a multiwafer reactor on sapphire and SiC substrates. The insulating properties of the GaN buffer...
Baeumler, M., Müller, S., Köhler, K., Wagner, J.
AlGaN/GaN heterostructures for power applications, grown on sapphire substrates by metal organic vapor phase epitaxy (MOVPE) in a multiwafer reactor were analyzed by spectroscopic ellipsometry (SE)....
Optical evaluation of spatial carrier concentration fluctuations in doped InP substrates (2003)
Baeumler, M., Diwo, E., Jantz, W., Sahr, U., Müller, G., Grant, I.
Nondestructive electrical characterization of LEC and VGF grown InP:S substrates is achieved with innovative photoluminescence line shift topography. The optical data, satisfactorily in agreement...
Sahr, U., Mueller, G., Grant, I., Baeumler, M., Jantz, W.
S-doped InP crystals were grown in a VGF furnace. The substrates, cut from the seed, middle and tail portions of the ingot, were investigated by Hall-measurement, photoluminescence spectroscopy and...
Photoluminescence topography, PICTS and microwave conductivity investigation of EL6 in GaAs (2002)
Steinegger, T., Gründig-Wendrock, B., Baeumler, M., Jurisch, M., Jantz, W., Niklas, J.
Further evidence was found that the 0.8 eV luminescence band in GaAs is correlated to the EL6 defect as identified by photo induced current transient spectroscopy (PICTS). From luminescence...
2K PL topography of silicon doped VGf-GaAs wafers (2002)
Baeumler, M., Maier, M., Herres, N., Bünger, T., Stenzenberger, J., Jantz, W.
We report on full wafer and small area photoluminescence topography investigations of VGF GaAs:Si wafers. The wavelength-specific images exhibit various correlations and anti-correlations. Intensity...
Malyarchuk, V., Tomm, J., Lienau, C., Rinner, F., Baeumler, M.
We use a near-field microscopic technique to probe photoluminescence from the edge area of a quantum well. Near the edge, surface recombination gives rise to a gradual variation of the...
Quantitative topographic assessment of Cu incorporation in GaAs (2000)
Baeumler, M., Stibal, R., Stolz, W., Steinegger, T., Jurisch, M., Maier, M., ...
The modification of the bulk resistivity of semi-insulating GaAs caused by incorporation of copper has been studied. Wafers cut from an ingot annealed, intentionally Cu contaminated LEC grown crystal...
Facet degradation of high-power diode laser arrays (2000)
Tomm, J.W., Thamm, E., Bärwolff, A., Elsässer, T., Luft, J., Baeumler, M., ...
Micro-Raman facet temperatures of high-power diode lasers with different waveguide architectures are compared. For regular operation conditions, the thermal behavior of "unaged" arrays emitting in...
Optical and structural analysis of degraded high power InGaAlAs/AlGaAs lasers (1999)
Frigeri, C., Baeumler, M., Migliori, A., Weyher, J.L., Jantz, W.
The failure of high power InGaAlAs/AlGaAs double quantum well (DQW) lasers has been studied by plan-view photoluminescence (PL), cross sectional (002) dark field TEM and X-ray microanalysis. The...
Baeumler, M., Weinberg, U., Wagner, J., Jantz, W.
The assessment of the lateral homogeneity of substrates and epitaxial layers requires techniques that are capable of measuring he full wafer area as well as microscopic defect structures. Optical...
Investigation of degraded laser diodes by chemical preparation and luminescence microscopy (1998)
Baeumler, M., Weyher, J.L., Müller, S., Jantz, W., Stibal, R., Herrmann, G., ...
The gradual degradation of 808 nm InGaAlAs/AlGaAs and 940 nm InGaAs/AlGaAs high power laser diodes has been investigated by plane view photoluminescence microscopy of the active layer. 940 nm lasers...
Cross-sectional TEM study of degraded high power diode lasers (1998)
Frigeri, C., Weyher, J.L., Baeumler, M., Müller, S., Jantz, W., Luft, J., ...
Cross-sectional TEM has been applied to the study of defects in degraded InGaAs/AlGaAs double quantum well (QW) diode lasers. The degradation is due to the formation of a dense band of extrinsic...
Influence of multi wafer annealing of LEC GaAs substrates on the quality of epitaxial layers (1996)
Forker, J., Baeumler, M., Weyher, J.L., Jantz, W., Bernklau, D., Riechert, H., ...
The lateral distribution of dislocations and nonradiative recombination centers in buik LEC GaAs is reproduced in the epilayer. Combined ingot/multi wafer annealing reduces the excess As...
Bürkner, S., Baeumler, M., Wagner, J., Larkins, E.C., Rothemund, W., Ralston, J.D.
Interdiffusion has been investigated in molecular-beam epitaxially (MBE)-grown, highly strained ln(ind 0.35)Ga(ind o.65)As/GaAs multiple quantum well (MQW) structures. Thermal intermixing and...
Bürkner, S., Larkins, E.C., Baeumler, M., Wagner, J., Rothemund, W., Flemig, G., ...
The cap layer dependence and selectivity of impurity free interdiffusion in molecular beam epitaxially grown pseudomorphic InyGa1-yAs/GaAs multiple quantum well structures with y=0.2 and 0.35 have...
Larkins, E.C., Benz, W., Esquivias, I., Rothemund, W., Baeumler, M., Weisser, S., ...
We present results from In sub0.35 Ga sub 0.65 As-GaAs 4 QW lasers whose Al sub0.8 Ga sub0.2 As binary short-period superlattice (SPSL) cladding layers were grown at either 700 degree Celsius or 620...
Flemig, G.W., Brenn, R., Larkins, E.C., Bürkner, S., Bender, G., Baeumler, M., ...
Dechanneling and angular scan measurements with 2 MeV high4 He highplus ions have been performed to investigate molecular-beam epitaxially (MBE)-grown strained In suby Ga sub 1-y As/GaAs single...
Baeumler, M., Larkins, E.C., Bachem, K.H., Bernklau, D., Riechert, H., Ralston, J.D., ...
Nonradiative recombination centers in epitaxial heterostructures are studied with spectrally selective photoluminescence microscopy (PLM). Characteristic patterns of the dislocation density...
Photoluminescence microscopy investigation of lattice defects in epitaxial heterostructures (1993)
Wang, Z.M., Baeumler, M., Jantz, W., Bachem, K.H., Larkins, E.C., Ralston, J.D.
Spectrally selective photoluminescence microscopy has been used to investigate non-radiative defects and crystal imperfections in lattice-matched AlGaAs/GaAs quantum well structures grown by...
Haight, R., Baeumler, M., Silberman, J.A., Kirchner, P.D.
The technique of subpicosecond angle-resolved laser photoemission spectroscopy is described. Investigations of the dynamics of electrons excited into normally unoccupied states at the cleaved GaAs...
Ultrafast-electron dynamics and recombination on the Ge(111)(2x1) pi-bonded surface (1992)
Angle-resolved laser-photoemission spectroscopy has been used to study the ultrafast-electron scattering and recombination processes on the Ge(111) pi-bonded (2 x 1) surface with subpicosecond time...
Renormalization of the one-dimensional pi-pi band gap on the Ge -111- 2x1 surface. (1992)
Using angle resolved laser photoemission spectroscopy we have measured the transient narrowing of the surface state band gap on the cleaved Ge(111) 2 x 1 surface. The reconstruction of this surface...
Photoluminescence microscopy investigation of lattice defects in epitaxial heterostructures (1992)
Wang, Z.M., Baeumler, M., Jantz, W., Bachem, K.H., Larkins, E.C., Ralston, J.D.
Omling, P., Hofmann, D.M., Baeumler, M., Kaufmann, U., Kunzer, M.
In an investigation of GaAs doped with Sb to a concentration of approximately equal to 1 x 10high19 cmhighminus3, the electron-paramagnetic-resonance (EPR) signal of the SbsubGa heteroantisite defect...
The role of deep acceptors for the compensation of undoped SI GaAs: Chapter 1 (1990)
Baeumler, M., Mooney, P., Kaufmann, U., Wagner, J.
The equilibrium concentrations of singly ionized AsGa/EL2 have been found to exceed the shallow acceptor (C and Zn) concentrations in two series of LEC pBN-GaAs samples. This finding is attributed to...
Optical properties of the SbGa heteroantisite defect in GaAs:Sb (1989)
Baeumler, M., Fuchs, F., Kaufmann, U.
Photoelectron-paramagnetic-resonance and near-infrared-absorption measurements on antimony-doped GaAs:Sb are reported. The results provide convincing evidence that the E sub c - 0.48 eV level in this...
Baeumler, M., Schneider, J., Kaufmann, U., Meyer, B.
Both neutral (A0) and ionized (A minus) manganese acceptor states in p-GaAs:Mn were analysed by optically detected magnetic resonance (ODMR) via ESR-induced changes in the magnetic circular dichroism...
Electron parametric resonance identification of the SbGa heteroantisite defect in GaAs:Sb (1989)
Baeumler, M., Schneider, J., Mitchel, W.C., Yu, P.W., Kaufmann, U.
GaAs doped with antimony (Sb) to a level of 10 high 19 cm high minus 3 has been studied by electron paramagnetic resoncance (EPR). A new EPR spectrum has been discovered which is identified as the Sb...
Baeumler, M., Mooney, P.M., Kaufmann, U.
A new photoexcitation band of the FR3 EPR signal in undoped semiinsulating GaAs has been discovered. It results from the excitation of an electron from the FR3 acceptor level to the conduction band....
Photoresponse of the FR3 electron-spin-resonance signal in GaAs (1987)
Wilkening, W., Baeumler, M., Kaufmann, U.
The photoresponse of the FR3 electron-spin-resonance (ESR) signal in GaAs has been studied. Excitation and quenching of the FR3 ESR is shown to result from the optically induced charge exchange...
Electronic structure of the neutral manganese acceptor in gallium arsenide (1987)
Schneider, J., Wilkening, W., Baeumler, M., Köhl, F., Kaufmann, U.
A new manganese-related isotropic electron-spin-resonance signal at g=2.77 has been observed in GaAs. It is shown to arise from the neutral Mn acceptor, MnE0. The analysis gives an answer to the...
Electron spin resonance of erbium in gallium arsenide (1987)
Baeumler, M., Schneider, J., Köhl, F., Tomzig, E.
Electron spin resonance (ESR) has been detected for erbium, Er(4f11), in gallium arsenide. The ESR spectrum was found to be isotropic, with a hyperfine splitting of A(167Er)=208x10 E-4/cm and a...
Identifizierung und Charakterisierung von Punktdefekten in GaAs und InP (1986)
Baeumler, M., Pomrenke, G., Schneider, J., Kaufmann, U., Müller, H., Ennen, H., ...
Photo-EPR of defects in undoped semiinsulating GaAs (1986)
Baeumler, M., Wilkening, W., Kaufmann, U., Windscheif, J.
Electron paramagnetic resonance spectra of as-grown, semi-insulating LEC GaAs at 9 GHz and 35 GHz have revealed three high intensity signals presumably associated with acceptor type defects. The...
New photosensitive EPR signals in undoped semi-insulating GaAs (1986)
Baeumler, M., Kaufmann, U., Windscheif, J.
Three new EPR signals labelled FR1, FR2 and FR3 have been observed in undoped as grown LEC GaAs. They are well observable only below 10K, their intensities are high and they appear only after optical...
Baeumler, M., Wilkening, W., Kaufmann, U., Windscheif, J.
Electron paramagnetic resonance studies on as-grown semi-insulating liquid encapsulation Czochralski (LEC) GaAs at 35 GHz have revealed a new resonance labeled FR3. It is consistently present in LEC...