The yellow Luminescence in GaN centered at 2.2 eV has been studied in various epitaxial layers grown by MOVPE on sapphire and by the sandwich sublimation methode on 6H-SiC substrates. The photoluminescence and optically detected magnetic resonance results can be consistently explained by a recombination model involving shallow donors and deep donors.

We studied high purity GaAs grown by optically detected cyclotron resonance (ODCR) using microwave frequencies at 36 and 140 GHz. The samples were grown by the metalorganic vapor phase epitaxy (MOVPE) using nitrogen as a carrier gas. The ODCR linewidth which is a measure of the mobility of the sample is dominated by neutral impurity scattering at low temperatures (<10 K) and acoustic deformation potential scattering at higher temperatures (10 to 30 K). At 2 K we obtain a mobility of about 3 x 10(5) cm(2)/Vs, one of the best values for MOVPE grown GaAs. Upon reduction of the photoexcitation power, i.e. reducing the photo-neutralisation of impurities, ionized impurity scattering gives an additional contribution. At high microwave powers the ODCR properties change remarkably, and hot electron relaxation involving longitudinal optical phonon processes is observed.

We have investigated AlxGa1−xN /GaN heterostructures (0<x<0.22) grown by metal organic vapor phase epitaxy on sapphire with photoluminescence (PL), reflexion and cathodo-luminescence experiments. The energetic positions of the free A-exciton in GaN and AlGaN as a function of the alloy compositions are deduced from temperature dependent PL and from reflexion measurements. We obtain a small bowing parameter and no evidence for a Stokes shift between absorption and emission. The AlxGa1−xN films induce additional compressive strain on the underlying GaN film. Compositional inhomogeneities are present, but the fluctuations are too small to be important for carrier localisation. The broadening of the luminescence line width in the alloy can be described by statistical disorder of a random alloy.

AlGaN on GaN epitaxial films with Al contents between 6% and 76% were investigated by stationary photoluminescence experiments which allows to determine the dependence of the energy gap on alloy composition. The observed increase of the luminescence linewidth as a function of the Al molar fraction can be explained by alloy broadening. The localization energy of the bound exciton increases considerably and reaches a Value of 53 meV for 61% Al. It could imply that the donor binding energy would markedly deviate from its effective mass value, an unexpected result if the residual donor is Si.

physica status solidi (b)Volume 205, Issue 1 p. R7-R8 Rapid Research Note The Dependence of the Band Gap on Alloy Composition in Strained AlGaN on GaN G. Steude, G. Steude I. Physikalisches Institut, Universität Gießen, 35392 Gießen, GermanySearch for more papers by this authorD. M. Hofmann, D. M. Hofmann I. Physikalisches Institut, Universität Gießen, 35392 Gießen, GermanySearch for more papers by this authorB. K. Meyer, B. K. Meyer I. Physikalisches Institut, Universität Gießen, 35392 Gießen, GermanySearch for more papers by this authorH. Amano, H. Amano Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this authorI. Akasaki, I. Akasaki Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this author G. Steude, G. Steude I. Physikalisches Institut, Universität Gießen, 35392 Gießen, GermanySearch for more papers by this authorD. M. Hofmann, D. M. Hofmann I. Physikalisches Institut, Universität Gießen, 35392 Gießen, GermanySearch for more papers by this authorB. K. Meyer, B. K. Meyer I. Physikalisches Institut, Universität Gießen, 35392 Gießen, GermanySearch for more papers by this authorH. Amano, H. Amano Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this authorI. Akasaki, I. Akasaki Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this author First published: 29 January 1999 https://doi.org/10.1002/(SICI)1521-3951(199801)205:13.0.CO;2-7Citations: 14AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References 1 Q. Wang, Y. Yan, and R. Wang, phys. stat. sol. (a) 155, 289 (1996). 2 T. Takeuchi, H. Takeuchi, S. Sota, H. Sakai, H. Amano, and I. Akasaki, Jpn. J. Appl. Phys. 36, L 177 (1997). 3 S. Yoshida, S. Misawa, and S. Gonda, J. Appl. Phys. 53, 6844 (1982). 4 Y. Koide, H. Itoh, M. R. H. Khan, K. Hiramatsu, and N. Sawaki, J. Appl. Phys. 61, 4540 (1987). 5 D. K. Wickendem, C. B. Bargeron, W. A. Bryden, J. Miragliova, and T. J. Kistenmacher, Appl. Phys. Lett. 65, 2024 (1994). 6 W. Rieger, T. Metzger, H. Angerer, R. Dimitrov, O. Ambacher, and M. Stutzmann, Appl. Phys. Lett. 68(7), 970 (1996). 7 H. Angerer, D. Brunner, F. Freudenberg, O. Ambacher, M. Stutzmann, R. Höpler, T. Metzger, E. Born, G. Dollinger, A. Bergmaier, S. Karsch, and H.-J. Körner, Appl. Phys. Lett. 71 ((11), 1504 (1997). Citing Literature Volume205, Issue1January 1998Pages R7-R8 ReferencesRelatedInformation

We studied the recombination at about 3.410eV in nominally undoped GaN and highly oxygen-doped GaN by photoluminescence (PL) and cathodoluminescence (CL). For this line we find an upper limit for the thermal activation energy of EA⩽21±3meV. In time-resolved PL, lifetimes of 300–480ps are observed indicating excitonic recombination. The defect giving rise to this emission can be created by Ar+ ion implantation. In conclusion, the 3.410eV luminescence is attributed to excitons bound to structural defects in hexagonal GaN.

physica status solidi (a)Volume 165, Issue 2 p. R3-R4 Rapid Research Note The Residual Donor Binding Energy in AlGaN Epitaxial Layers G. Steude, G. Steude I. Physikalisches Institut, Universität Giessen, D-35392 Giessen, GermanySearch for more papers by this authorD. M. Hofmann, D. M. Hofmann I. Physikalisches Institut, Universität Giessen, D-35392 Giessen, GermanySearch for more papers by this authorB. K. Meyer, B. K. Meyer I. Physikalisches Institut, Universität Giessen, D-35392 Giessen, GermanySearch for more papers by this authorH. Amano, H. Amano Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this authorI. Akasaki, I. Akasaki Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this author G. Steude, G. Steude I. Physikalisches Institut, Universität Giessen, D-35392 Giessen, GermanySearch for more papers by this authorD. M. Hofmann, D. M. Hofmann I. Physikalisches Institut, Universität Giessen, D-35392 Giessen, GermanySearch for more papers by this authorB. K. Meyer, B. K. Meyer I. Physikalisches Institut, Universität Giessen, D-35392 Giessen, GermanySearch for more papers by this authorH. Amano, H. Amano Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this authorI. Akasaki, I. Akasaki Department of Electrical and Electronic Engineering, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468, JapanSearch for more papers by this author First published: 29 January 1999 https://doi.org/10.1002/(SICI)1521-396X(199802)165:23.0.CO;2-HCitations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume165, Issue2February 1998Pages R3-R4 RelatedInformation

GaN films were grown epitaxially on sapphire and 6H-SiC substrates by low-pressure chemical vapor deposition (LPCVD) using gallium(III) chloride and ammonia as gallium and nitrogen precursor, respectively. The properties of these samples were examined by X-ray diffraction, Hall effect measurements, secondary-ion mass spectroscopy (SIMS) and photoluminescence (PL). All GaN layers exhibit high free carrier concentrations between n=2×1018 and 5×1019cm−3 caused by unintentional n-type doping. We provide evidence that this high unintentionally doping is linked to the oxygen content in the films. The correlation between the optical properties with respect to position and line shape of the band-edge luminescence and the electrical properties, i.e. the free carrier concentration, is discussed.

We investigated the influence of the growth temperature on high temperature vapor phase epitaxy of GaN. An almost direct proportionality between the growth rate and the Ga vapor pressure is observed. At optimum conditions growth rates as high as 210 μm/h (T=1150°c) are achieved. The maximum growth rate is believed to be limited by the supply of ammonia and the starting composition of GaN. Under optimum GaN growth conditions AlGaN layers were grown starting from previously alloyed Al-Ga as well as from co-evaporation of Ga and Al. Adding Al leads to a significant reduction of growth rate and increases the homogeneity of the layers. However, in almost all cases phase separation is found. Besides the binary GaN and AlN phases an intermediate AlGaN phase appears

We report on the optical, electrical and structural properties of GaN films heteroepitaxially grown by low pressure chemical vapor deposition on 6H-SiC substrates. We employed photoluminescence (PL), Hall effect measurements, scanning tunneling microscopy (STM) and X-ray analysis to determine the quality of our films. Heterojunction diodes were fabricated on p-type SiC and characterized by temperature dependent current–voltage and capacitance–voltage techniques. The results are interpreted within the thermionic emission model and the barrier found is attributed to the conduction band offset between 6H-SiC and wurtzite GaN. The diodes show electroluminescence of the donor-acceptor pair recombination type of 6H-SiC at room temperature. By analysis of the injection behavior we can interpret our data, determining the high valence band offset between 6H-SiC and α-GaN to 0.67 eV. This high valence band offset favors applications for hetero-bipolar transistors (HBT).

High purity GaAs grown by metal organic vapor phase epitaxy (MOVPE) using nitrogen as a carrier gas has been studied by optically detected cyclotron resonance (ODCR) at microwave and far infrared frequencies. Upon variation of the experimental parameters such as sample temperature, optical excitation density and microwave power the residual ionized (donor) and neutral (acceptor) impurity concentrations can be estimated, they are 2×1012 cm-3 and 5×1013 cm-3, respectively. The luminescence results indicate C to be the dominant residual acceptor. The residual donors were identified as S, Se, Sn from the observation of the internal 1s - 3p- transitions, with S showing the highest absorption strength. At low temperatures the electron mobility as determined by ODCR is about 3×105 cm2/Vs.

We studied ZnSe single quantum wells with well widths from 4 to 1 nm by optically detected cyclotron resonance (ODCR). In the samples grown by metal organic vapour phase epitaxy, where the residual shallow donor concentration is still of the order of mid 1016 cm−3, we find maximum electron mobilities of 46 000 cm2/V·s at low temperatures. The mechanism causing the cyclotron resonances to be observed in the luminescence is dominantly an energy transfer by heating the crystal lattice.

Photoluminescence, time-integrated, time-resolved, and photoluminescence excitation spectroscopy have been employed to study the 2.2 eV ('yellow'') emission in undoped GaN epitaxial layers. It is best described by a recombination model involving shallow donors and deep donors of probably intrinsic origin. Optically detected magnetic resonance reveals the participation of the shallow donor based on the analysis of the g value and Lorentzian line shape.