C. Hallin - Academia.edu (original) (raw)

Papers by C. Hallin

Research paper thumbnail of Optically detected magnetic resonance studies of defects in electron-irradiated 3C SiC layers

Physical Review B, 1997

Defects in electron-irradiated 3C SiC were studied by optically detected magnetic resonance (ODMR... more Defects in electron-irradiated 3C SiC were studied by optically detected magnetic resonance (ODMR). In addition to the isotropic L2 center previously reported, an ODMR spectrum labeled L3, with a trigonal symmetry and an effective electron spin S=1, was observed after annealing at ~750 °C. The g values of the center along and perpendicular to the trigonal axis were determined as

Research paper thumbnail of CVD-Growth of Low-Doped 6H SIC Epitaxial Films

Research paper thumbnail of Formation of Ni-graphite intercalation compounds on SiC

Research paper thumbnail of Silicon Carbide Hot-Wall Epitaxy for Large-Area, High-Voltage Devices

MRS Proceedings, 2008

ABSTRACT The growth of thick silicon carbide (SiC) epitaxial layers for large-area, high-power de... more ABSTRACT The growth of thick silicon carbide (SiC) epitaxial layers for large-area, high-power devices is described. Horizontal hot-wall epitaxial reactors with a capacity of three, 3-inch wafers have been employed to grow over 350 epitaxial layers greater than 100 μm ...

Research paper thumbnail of Characterization and Comparison of 4H-SiC(1120) and 4H-SiC(0001) 8° Off-Axis Substrates and Homoepitaxial Films

Research paper thumbnail of Hole effective masses in 6H-SiC from optically detected cyclotron resonance

Physical Review B, 2002

ABSTRACT

Research paper thumbnail of Ga-bound excitons in 3C-, 4H-, and 6H-SiC

Research paper thumbnail of Optical investigation of Fermi-edge singularities in Al0.35Ga0.65As/GaAs heterostructures

Physical Review B, 1992

Many-body effects of two-dimensional electrons in n-type modulation-doped AlxGa1-xAs/GaAs heteros... more Many-body effects of two-dimensional electrons in n-type modulation-doped AlxGa1-xAs/GaAs heterostructures have been studied by photoluminescence (PL), PL excitation (PLE) spectroscopy, and optically detected cyclotron resonance (ODCR). A Fermi-edge singularity (FES) is observed both in PL and PLE spectra when a gate voltage is applied. Strong enhancements occur for electrons at the Fermi edge (EF) recombining both with holes bound at

Research paper thumbnail of Optically detected magnetic resonance studies of defects in 3C SiC epitaxial layers

Diamond and Related Materials, 1997

ABSTRACT Optically detected magnetic resonance (ODMR) was used to study defects in 3C SiC epitaxi... more ABSTRACT Optically detected magnetic resonance (ODMR) was used to study defects in 3C SiC epitaxial layers grown at high temperatures (1550°C) by chemical vapour deposition on a free-standing 3C SiC film substrate. An isotropic, very broad and asymmetric ODMR line was observed under ultraviolet light excitation. This line is shown to be due to the overlapping of two different isotropic spectra, as revealed by magnetic field modulation measurements. Both spectra can be described by an effective electron spin S = 12. The higher field line with a g-value of 2.006 may be related to a silicon vacancy. Using below bandgap excitation, the lower field spectrum (g = 2.012) was found to have a triplet structure which could be due to the hyperfine of 14N. This defect is related to a new photoluminescence band in the region of 1.1–1.58 eV.

Research paper thumbnail of Optically detected magnetic resonance studies of intrinsic defects in 6H-SiC

Semiconductor Science and Technology, 1999

Research paper thumbnail of Silicon vacancy related defect in 4H and 6H SiC

Physical Review B, 2000

ABSTRACT We report on an irradiation-induced photoluminescence (PL) band in 4H and 6H SiC and the... more ABSTRACT We report on an irradiation-induced photoluminescence (PL) band in 4H and 6H SiC and the corresponding optically detected magnetic resonance (ODMR) signals from this band. The deep PL band has the same number of no-phonon lines as there are inequivalent sites in the respective polytype. These lines are at 1352 and 1438 meV in the case of 4H and at 1366, 1398, and 1433 meV in the case of 6H. The intensity of the PL lines is reduced after a short anneal at 750 °C. ODMR measurements with above-band-gap excitation show that two spin-triplet (S=1) states with a weak axial character are detected via each PL line in these bands. One of these two triplet states can be selectively excited with the excitation energy of the corresponding PL line. These triplet signals can therefore be detected separately and only then can the well documented and characteristic hyperfine interaction of the silicon vacancy in SiC be resolved. Considering the correlation between the irradiation dose and the signal strength, the well established annealing temperature and the characteristic hyperfine pattern, we suggest that this PL band is related to the isolated silicon vacancy in 4H and 6H SiC. The spin state (S=1) implies a charge state of the vacancy with an even number of electrons. By combining the knowledge from complementary electron-spin resonance measurements and theoretical calculations we hold the neutral charge state for the strongest candidate.

Research paper thumbnail of Electronic structure of the neutral silicon vacancy in 4H and 6H SiC

Physical Review B, 2000

Detailed information about the electronic structure of the lowest-lying excited states and the gr... more Detailed information about the electronic structure of the lowest-lying excited states and the ground state of the neutral silicon vacancy in 4H and 6H SiC has been obtained by high-resolution photoluminescence (PL), PL excitation (PLE), and Zeeman spectroscopy of both PL and PLE. The excited states and the ground states involved in the characteristic luminescence of the defect with no-phonon (NP) lines at 1.438 and 1.352 eV in 4H SiC and 1.433, 1.398, and 1.368 eV in 6H SiC are shown to be singlets. The orbital degeneracy of the excited states is lifted by the crystal field for the highest-lying NP lines corresponding to one of the inequivalent lattice sites in both polytypes, leading to the appearance of hot lines at slightly higher energies. Polarization studies of the NP lines show a different behavior for the inequivalent sites. A comparison of this behavior in the two polytypes together with parameters from spin resonance studies provides useful hints for the assignment of the no-phonon lines to the inequivalent sites. In strained samples an additional fine structure of the NP lines can be resolved. This splitting may be due to strain variations in the samples.

Research paper thumbnail of Ligand hyperfine interaction at the neutral silicon vacancy in 4H- and 6H-SiC

Physical Review B, 2002

The silicon vacancy in its neutral charge state (VSi) has been unambiguously identified in 4H- an... more The silicon vacancy in its neutral charge state (VSi) has been unambiguously identified in 4H- and 6H-SiC. This was achieved by observation of ligand hyperfine interaction with the four carbon atoms in the nearest-neighbor shell and the twelve silicon atoms in the next-nearest-neighbor shell surrounding the vacancy. The complete hyperfine tensors have been determined for the V0Si center residing at

Research paper thumbnail of Performance of III-nitride epitaxy in a low V-to-III gas-flow ratio range under nitrogen ambient in a hot-wall MOCVD system

physica status solidi (c), 2005

Research paper thumbnail of Hole effective masses in 4H SiC

Physical Review B, 2000

Optically detected cyclotron resonance (ODCR) at X-band frequency (~9.23 GHz) was used to study h... more Optically detected cyclotron resonance (ODCR) at X-band frequency (~9.23 GHz) was used to study hole effective masses in 4H SiC. In addition to the known ODCR signal related to the cyclotron resonance (CR) of electrons we have observed an ODCR peak at a higher magnetic field, which is attributed to the CR of holes. In the vicinity of the maximum of the uppermost valence band, the constant energy surface can be considered as an ellipsoid with the principal axis along the c axis and the effective masses of the holes were determined as mh⊥=(0.66+/-0.02)m0 and mh||=(1.75+/-0.02)m0. The influence of the polaron coupling effect on the effective mass values in 4H SiC is discussed.

Research paper thumbnail of Optically detected magnetic resonance studies of intrinsic defects in 6H-SiC

Semiconductor Science and Technology, 1999

Research paper thumbnail of Radiative recombination in doped AlGaAs/GaAs heterostructures

Semiconductor Science and Technology, 1990

The radiative recombination processes of two-dimensional (2D) carriers have been studied for n-ch... more The radiative recombination processes of two-dimensional (2D) carriers have been studied for n-channel AlGaAs/GaAs heterojunctions with different doping levels. The recombination involving the 2D carriers confined on the GaAs side of the interface notch gives rise to two different photoluminescence (PL) bands, the so-called H-bands. A considerable variation of these bands in PL spectra is observed concerning shape, broadening, energy position and decay times. This variation depends on the experimental conditions, such as the temperature, intensity and photon energy of the excitation, but also on the design of the sample. Also, the dependence on these parameters is different for the two H-bands. The results are consistent with a general model for the origin of the two H-bands in n-channel heterojunctions as due to the recombination between 2D electrons confined in the GaAs notch and holes from either the valence band or the neutral acceptors in the active GaAs layer. The observed variations are explained as due to a corresponding variation in the band bending across the active GaAs layer. The spatial separation between the holes and the electrons involved in the H-band recombination processes depends critically on this band bending.

Research paper thumbnail of Growth of SiC by ?Hot-Wall? CVD and HTCVD

physica status solidi (b), 1997

A reactor concept for the growth of high-quality epitaxial SiC films has been investigated. The r... more A reactor concept for the growth of high-quality epitaxial SiC films has been investigated. The reactor concept is based on a hot-wall type susceptor which, due to the unique design, is very power efficient. Four different susceptors are discussed in terms of quality and uniformity ...

Research paper thumbnail of Hot-wall MOCVD grown homoepitaxial GaN layers with intense intrinsic excitonic structure

physica status solidi (a), 2005

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ... Hot-wall MOCVD grown homoepitaxial GaN ... more © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ... Hot-wall MOCVD grown homoepitaxial GaN layers with intense intrinsic excitonic structure ... A. Kakanakova-Georgieva*, IG Ivanov, C. Hallin, and E. Janzén Department of Physics and Measurement Technology, ...

Research paper thumbnail of Scanning spreading resistance microscopy of aluminum implanted 4H–SiC

Materials Science and Engineering: B, 2003

Research paper thumbnail of Optically detected magnetic resonance studies of defects in electron-irradiated 3C SiC layers

Physical Review B, 1997

Defects in electron-irradiated 3C SiC were studied by optically detected magnetic resonance (ODMR... more Defects in electron-irradiated 3C SiC were studied by optically detected magnetic resonance (ODMR). In addition to the isotropic L2 center previously reported, an ODMR spectrum labeled L3, with a trigonal symmetry and an effective electron spin S=1, was observed after annealing at ~750 °C. The g values of the center along and perpendicular to the trigonal axis were determined as

Research paper thumbnail of CVD-Growth of Low-Doped 6H SIC Epitaxial Films

Research paper thumbnail of Formation of Ni-graphite intercalation compounds on SiC

Research paper thumbnail of Silicon Carbide Hot-Wall Epitaxy for Large-Area, High-Voltage Devices

MRS Proceedings, 2008

ABSTRACT The growth of thick silicon carbide (SiC) epitaxial layers for large-area, high-power de... more ABSTRACT The growth of thick silicon carbide (SiC) epitaxial layers for large-area, high-power devices is described. Horizontal hot-wall epitaxial reactors with a capacity of three, 3-inch wafers have been employed to grow over 350 epitaxial layers greater than 100 μm ...

Research paper thumbnail of Characterization and Comparison of 4H-SiC(1120) and 4H-SiC(0001) 8° Off-Axis Substrates and Homoepitaxial Films

Research paper thumbnail of Hole effective masses in 6H-SiC from optically detected cyclotron resonance

Physical Review B, 2002

ABSTRACT

Research paper thumbnail of Ga-bound excitons in 3C-, 4H-, and 6H-SiC

Research paper thumbnail of Optical investigation of Fermi-edge singularities in Al0.35Ga0.65As/GaAs heterostructures

Physical Review B, 1992

Many-body effects of two-dimensional electrons in n-type modulation-doped AlxGa1-xAs/GaAs heteros... more Many-body effects of two-dimensional electrons in n-type modulation-doped AlxGa1-xAs/GaAs heterostructures have been studied by photoluminescence (PL), PL excitation (PLE) spectroscopy, and optically detected cyclotron resonance (ODCR). A Fermi-edge singularity (FES) is observed both in PL and PLE spectra when a gate voltage is applied. Strong enhancements occur for electrons at the Fermi edge (EF) recombining both with holes bound at

Research paper thumbnail of Optically detected magnetic resonance studies of defects in 3C SiC epitaxial layers

Diamond and Related Materials, 1997

ABSTRACT Optically detected magnetic resonance (ODMR) was used to study defects in 3C SiC epitaxi... more ABSTRACT Optically detected magnetic resonance (ODMR) was used to study defects in 3C SiC epitaxial layers grown at high temperatures (1550°C) by chemical vapour deposition on a free-standing 3C SiC film substrate. An isotropic, very broad and asymmetric ODMR line was observed under ultraviolet light excitation. This line is shown to be due to the overlapping of two different isotropic spectra, as revealed by magnetic field modulation measurements. Both spectra can be described by an effective electron spin S = 12. The higher field line with a g-value of 2.006 may be related to a silicon vacancy. Using below bandgap excitation, the lower field spectrum (g = 2.012) was found to have a triplet structure which could be due to the hyperfine of 14N. This defect is related to a new photoluminescence band in the region of 1.1–1.58 eV.

Research paper thumbnail of Optically detected magnetic resonance studies of intrinsic defects in 6H-SiC

Semiconductor Science and Technology, 1999

Research paper thumbnail of Silicon vacancy related defect in 4H and 6H SiC

Physical Review B, 2000

ABSTRACT We report on an irradiation-induced photoluminescence (PL) band in 4H and 6H SiC and the... more ABSTRACT We report on an irradiation-induced photoluminescence (PL) band in 4H and 6H SiC and the corresponding optically detected magnetic resonance (ODMR) signals from this band. The deep PL band has the same number of no-phonon lines as there are inequivalent sites in the respective polytype. These lines are at 1352 and 1438 meV in the case of 4H and at 1366, 1398, and 1433 meV in the case of 6H. The intensity of the PL lines is reduced after a short anneal at 750 °C. ODMR measurements with above-band-gap excitation show that two spin-triplet (S=1) states with a weak axial character are detected via each PL line in these bands. One of these two triplet states can be selectively excited with the excitation energy of the corresponding PL line. These triplet signals can therefore be detected separately and only then can the well documented and characteristic hyperfine interaction of the silicon vacancy in SiC be resolved. Considering the correlation between the irradiation dose and the signal strength, the well established annealing temperature and the characteristic hyperfine pattern, we suggest that this PL band is related to the isolated silicon vacancy in 4H and 6H SiC. The spin state (S=1) implies a charge state of the vacancy with an even number of electrons. By combining the knowledge from complementary electron-spin resonance measurements and theoretical calculations we hold the neutral charge state for the strongest candidate.

Research paper thumbnail of Electronic structure of the neutral silicon vacancy in 4H and 6H SiC

Physical Review B, 2000

Detailed information about the electronic structure of the lowest-lying excited states and the gr... more Detailed information about the electronic structure of the lowest-lying excited states and the ground state of the neutral silicon vacancy in 4H and 6H SiC has been obtained by high-resolution photoluminescence (PL), PL excitation (PLE), and Zeeman spectroscopy of both PL and PLE. The excited states and the ground states involved in the characteristic luminescence of the defect with no-phonon (NP) lines at 1.438 and 1.352 eV in 4H SiC and 1.433, 1.398, and 1.368 eV in 6H SiC are shown to be singlets. The orbital degeneracy of the excited states is lifted by the crystal field for the highest-lying NP lines corresponding to one of the inequivalent lattice sites in both polytypes, leading to the appearance of hot lines at slightly higher energies. Polarization studies of the NP lines show a different behavior for the inequivalent sites. A comparison of this behavior in the two polytypes together with parameters from spin resonance studies provides useful hints for the assignment of the no-phonon lines to the inequivalent sites. In strained samples an additional fine structure of the NP lines can be resolved. This splitting may be due to strain variations in the samples.

Research paper thumbnail of Ligand hyperfine interaction at the neutral silicon vacancy in 4H- and 6H-SiC

Physical Review B, 2002

The silicon vacancy in its neutral charge state (VSi) has been unambiguously identified in 4H- an... more The silicon vacancy in its neutral charge state (VSi) has been unambiguously identified in 4H- and 6H-SiC. This was achieved by observation of ligand hyperfine interaction with the four carbon atoms in the nearest-neighbor shell and the twelve silicon atoms in the next-nearest-neighbor shell surrounding the vacancy. The complete hyperfine tensors have been determined for the V0Si center residing at

Research paper thumbnail of Performance of III-nitride epitaxy in a low V-to-III gas-flow ratio range under nitrogen ambient in a hot-wall MOCVD system

physica status solidi (c), 2005

Research paper thumbnail of Hole effective masses in 4H SiC

Physical Review B, 2000

Optically detected cyclotron resonance (ODCR) at X-band frequency (~9.23 GHz) was used to study h... more Optically detected cyclotron resonance (ODCR) at X-band frequency (~9.23 GHz) was used to study hole effective masses in 4H SiC. In addition to the known ODCR signal related to the cyclotron resonance (CR) of electrons we have observed an ODCR peak at a higher magnetic field, which is attributed to the CR of holes. In the vicinity of the maximum of the uppermost valence band, the constant energy surface can be considered as an ellipsoid with the principal axis along the c axis and the effective masses of the holes were determined as mh⊥=(0.66+/-0.02)m0 and mh||=(1.75+/-0.02)m0. The influence of the polaron coupling effect on the effective mass values in 4H SiC is discussed.

Research paper thumbnail of Optically detected magnetic resonance studies of intrinsic defects in 6H-SiC

Semiconductor Science and Technology, 1999

Research paper thumbnail of Radiative recombination in doped AlGaAs/GaAs heterostructures

Semiconductor Science and Technology, 1990

The radiative recombination processes of two-dimensional (2D) carriers have been studied for n-ch... more The radiative recombination processes of two-dimensional (2D) carriers have been studied for n-channel AlGaAs/GaAs heterojunctions with different doping levels. The recombination involving the 2D carriers confined on the GaAs side of the interface notch gives rise to two different photoluminescence (PL) bands, the so-called H-bands. A considerable variation of these bands in PL spectra is observed concerning shape, broadening, energy position and decay times. This variation depends on the experimental conditions, such as the temperature, intensity and photon energy of the excitation, but also on the design of the sample. Also, the dependence on these parameters is different for the two H-bands. The results are consistent with a general model for the origin of the two H-bands in n-channel heterojunctions as due to the recombination between 2D electrons confined in the GaAs notch and holes from either the valence band or the neutral acceptors in the active GaAs layer. The observed variations are explained as due to a corresponding variation in the band bending across the active GaAs layer. The spatial separation between the holes and the electrons involved in the H-band recombination processes depends critically on this band bending.

Research paper thumbnail of Growth of SiC by ?Hot-Wall? CVD and HTCVD

physica status solidi (b), 1997

A reactor concept for the growth of high-quality epitaxial SiC films has been investigated. The r... more A reactor concept for the growth of high-quality epitaxial SiC films has been investigated. The reactor concept is based on a hot-wall type susceptor which, due to the unique design, is very power efficient. Four different susceptors are discussed in terms of quality and uniformity ...

Research paper thumbnail of Hot-wall MOCVD grown homoepitaxial GaN layers with intense intrinsic excitonic structure

physica status solidi (a), 2005

© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ... Hot-wall MOCVD grown homoepitaxial GaN ... more © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ... Hot-wall MOCVD grown homoepitaxial GaN layers with intense intrinsic excitonic structure ... A. Kakanakova-Georgieva*, IG Ivanov, C. Hallin, and E. Janzén Department of Physics and Measurement Technology, ...

Research paper thumbnail of Scanning spreading resistance microscopy of aluminum implanted 4H–SiC

Materials Science and Engineering: B, 2003