Phonons and Free Carriers in a Strained Hexagonal GaN-AlN Superlattice Measured by Infrared Ellipsometry and Raman Spectroscopy

1999 ◽  
Vol 595 ◽  
Author(s):  
M. Schubert ◽  
A. Kasic ◽  
T.E. Tiwald ◽  
J.A. Woollam ◽  
V. Harle ◽  
...  
Keyword(s):  
Carrier Mobility ◽  
Free Carrier ◽  
Phonon Modes ◽  
Lateral Mobility ◽  
Free Carriers ◽  
Organic Vapor ◽  
Infrared Ellipsometry ◽  
Order Of Magnitude ◽  
Metal Organic ◽  
Vertical Mobility

AbstractPhonon and free-carrier effects in a strained hexagonal (α) {GaN}l-{AlN}m superlattice (SL) heterostructure (l = 8 nm, m = 3 nm) are studied by infrared spectroscopic ellipsometry (IRSE) and micro (µ)-Raman scattering. Growth of the heterostructures was performed by metal-organic vapor phase epitaxy (MOVPE) on (0001) sapphire. An unstrained 1 µm-thick α-GaN layer was deposited prior to the SL. SL phonon modes are identified combining results from both IRSE and µ-Raman techniques. The shift of the GaN-sublayer phonon modes is used to estimate an average compressive SL stress of σxx ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×1018 cm−3 within the undoped SL GaN-sublayers. According to the vertical carrier confinement, the free-carrier mobility is anisotropic, and the lateral mobility ( µ⊥ ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (µ∥ ∼ 24 cm2/Vs, E∥c) by one order of magnitude.

scholarly journals Phonons and Free Carriers in a Strained Hexagonal GaN-AlN Superlattice Measured by Infrared Ellipsometry and Raman Spectroscopy

2000 ◽  
Vol 5 (S1) ◽  
pp. 710-716 ◽  
Author(s):  
M. Schubert ◽  
A. Kasic ◽  
T.E. Tiwald ◽  
J.A. Woollam ◽  
V. Härle ◽  
...  
Keyword(s):  
Carrier Mobility ◽  
Free Carrier ◽  
Phonon Modes ◽  
Lateral Mobility ◽  
Free Carriers ◽  
Organic Vapor ◽  
Infrared Ellipsometry ◽  
Order Of Magnitude ◽  
Metal Organic ◽  
Vertical Mobility

Phonon and free-carrier effects in a strained hexagonal (α) {GaN}l-{AlN}msuperlattice (SL) heterostructure (l = 8 nm, m = 3 nm) are studied by infrared spectroscopic ellipsometry (IRSE) and micro (µ)-Raman scattering. Growth of the heterostructures was performed by metal-organic vapor phase epitaxy (MOVPE) on (0001) sapphire. An unstrained 1 µm-thick α-GaN layer was deposited prior to the SL. SL phonon modes are identified combining results from both IRSE and µ-Raman techniques. The shift of the GaN-sublayer phonon modes is used to estimate an average compressive SL stress of σxx ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×1018 cm−3 within the undoped SL GaN-sublayers. According to the vertical carrier confinement, the free-carrier mobility is anisotropic, and the lateral mobility (µ⊥ ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (µ|| ∼ 24 cm2/Vs, E||c) by one order of magnitude.

The intrinsic free carrier mobility in AlGaN/GaN quantum wells

2004 ◽  
Vol 831 ◽  
Author(s):  
F. Carosella ◽  
M. Germain ◽  
J.-L. Farvacque
Keyword(s):  
Quantum Wells ◽  
Carrier Mobility ◽  
Electron System ◽  
Relaxation Mechanism ◽  
Free Carrier ◽  
Free Carriers ◽  
Scattering Mechanisms ◽  
Carrier Interaction ◽  
Scattering Strength ◽  
Two Bodies

ABSTRACTThe aim of this contribution is to determine theoretically the maximum mobility that can be expected in AlGaN/GaN quantum wells as soon as the free carriers are only submitted to intrinsic scattering mechanisms associated with phonons and the carrier-carrier interaction. In our model, we consider that the carrier-carrier two bodies collisions do not constitute by themselves a relaxation mechanism since they conserve the momentum and the energy of the electron system. Thus, we assume that the free carriers act only through their contribution to the dynamical dielectric response of the material and, at least, through their collective behavior resulting into plasmons which, when damped, constitute now a real relaxation mechanism. The full scattering strength is connected with the imaginary part of the total reversed dielectric function including the lattice and the free carrier contributions. This approach automatically includes the scattering mechanisms associated with hybrid phonon/plasmon particles.

scholarly journals Far-infrared spectroscopy of PbTe doped with iron

2002 ◽  
Vol 67 (6) ◽  
pp. 415-423 ◽  
Author(s):  
Pantelija Nikolic ◽  
K. Radulovic ◽  
D. Vasiljevic-Radovic ◽  
V. Blagojevic ◽  
B. Milosavljevic ◽  
...  
Keyword(s):  
Liquid Nitrogen ◽  
Carrier Mobility ◽  
Hole Concentration ◽  
Far Infrared ◽  
Liquid Nitrogen Temperature ◽  
Free Carrier ◽  
Small Concentration ◽  
Far Infrared Spectroscopy ◽  
Infrared Reflection ◽  
Order Of Magnitude

Far infrared reflection spectra, at room and liquid nitrogen temperature, of PbTe single crystals doped with iron are presented. Plasma minima were observed at about 160 cm?1 and 180 cm?1 for room and liquid nitrogen temperature, respectively. Using the reflectivity diagrams and their minima the values of the hole concentrations and their mobility at both temperatures were calculated and compared with galvanomagnetic measurements. All these results indicated that when PbTe is doped with a small concentration of Fe, the hole concentration is reduced by one order of magnitude and the free carrier mobility is larger when compared to pure PbTe.

scholarly journals Raman Determination of the Phonon Deformation Potentials in α-GaN

1996 ◽  
Vol 1 ◽  
Author(s):  
F. Demangeot ◽  
J. Frandon ◽  
M. A. Renucci ◽  
Olivier Briot ◽  
Bernard Gil ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Phonon Frequency ◽  
Biaxial Stress ◽  
Phonon Modes ◽  
Frequency Shifts ◽  
Pressure Coefficients ◽  
Organic Vapor ◽  
Metal Organic ◽  
Reflectance Data

Raman spectroscopy is used to study the effect of the built-in biaxial stress on the E2 and A1 (LO) q = 0 phonon modes of wurtzite GaN layers deposited by metal organic vapor phase epitaxy on (0001) sapphire substrate. By means of phonon frequency shifts, the biaxial pressure coefficients of the mode frequencies are determined and used to calculate the corresponding deformation potentials. Stress calibration has been performed using reflectance data.

scholarly journals Легированный кремнием GaSb, выращенный методом ГФЭМОС в широком диапазоне соотношений V/III

2021 ◽  
Vol 55 (10) ◽  
pp. 931
Author(s):  
Р.В. Левин ◽  
А.С. Власов ◽  
Б.В. Пушный
Keyword(s):  
Raman Scattering ◽  
Carrier Concentration ◽  
Vapor Phase ◽  
Free Carrier ◽  
Free Carrier Concentration ◽  
X Ray Diffraction ◽  
X Ray ◽  
Organic Vapor ◽  
Metal Organic ◽  
Si Doped

Charachterization of Si-doped GaSb epitaxial layers grown by metal organic vapor phase epitaxy is presented. Samples are grown at constant SiH4 flow with a TMSb/TEGa ratio ranged from 1 to 50. X-ray diffraction, Raman scattering, photoluminescence, resistivity, free carrier concentration and their mobility are studied.

The Influence of Nitrogen Position on Charge Carrier Mobility in Enantiopure Aza[6]helicene Crystals

2018 ◽  
Author(s):  
Francesco Salerno ◽  
Beth Rice ◽  
Julia Schmidt ◽  
Matthew J. Fuchter ◽  
Jenny Nelson ◽  
...  
Keyword(s):  
Solid State ◽  
Charge Carrier ◽  
Carrier Mobility ◽  
Chemical Structure ◽  
Crystal Packing ◽  
Charge Carrier Mobility ◽  
Individual Factor ◽  
Charge Mobility ◽  
Order Of Magnitude ◽  
Small Change

<p>The properties of an organic semiconductor are dependent on both the chemical structure of the molecule involved, and how it is arranged in the solid-state. It is challenging to extract the influence of each individual factor, as small changes in the molecular structure often dramatically change the crystal packing and hence solid-state structure. Here, we use calculations to explore the influence of the nitrogen position on the charge mobility of a chiral organic molecule when the crystal packing is kept constant. The transfer integrals for a series of enantiopure aza[6]helicene crystals sharing the same packing were analysed in order to identify the best supramolecular motifs to promote charge carrier mobility. The regioisomers considered differ only in the positioning of the nitrogen atom in the aromatic scaffold. The simulations showed that even this small change in the chemical structure has a strong effect on the charge transport in the crystal, leading to differences in charge mobility of up to one order of magnitude. Some aza[6]helicene isomers that were packed interlocked with each other showed high HOMO-HOMO integrals (up to 70 meV), whilst molecules arranged with translational symmetry generally afforded the highest LUMO-LUMO integrals (40 - 70 meV). As many of the results are not intuitively obvious, a computational approach provides additional insight into the design of new semiconducting organic materials.</p>

scholarly journals Low-frequency optical phonon modes and carrier mobility in the halide perovskite CH3NH3PbBr3 using terahertz time-domain spectroscopy

2017 ◽  
Vol 111 (20) ◽  
pp. 201903 ◽  
Author(s):  
Daming Zhao ◽  
Jonathan M. Skelton ◽  
Hongwei Hu ◽  
Chan La-o-vorakiat ◽  
Jian-Xin Zhu ◽  
...  
Keyword(s):  
Time Domain ◽  
Optical Phonon ◽  
Carrier Mobility ◽  
Low Frequency ◽  
Terahertz Time Domain Spectroscopy ◽  
Phonon Modes ◽  
Time Domain Spectroscopy ◽  
Halide Perovskite

Metal-organic vapor-phase epitaxial growth of HgCdTe device heterostructures on three-inch-diameter substrates

2003 ◽  
Vol 32 (7) ◽  
pp. 656-660 ◽  
Author(s):  
C. D. Maxey ◽  
J. P. Camplin ◽  
I. T. Guilfoy ◽  
J. Gardner ◽  
R. A. Lockett ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Vapor Phase ◽  
Organic Vapor ◽  
Metal Organic
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