Phonons and free-carrier properties of binary, ternary, and quaternary group-III nitride layers measured by Infrared Spectroscopic Ellipsometry

The infrared-optical properties of GaAs/GaNxAs1−x superlattice (SL) heterostructures (0 < x < 3.3%) are studied by variable angle-of-incidence infrared spectroscopic ellipsometry (IRSE) for wavenumbers from 250 cm−1 to 700 cm−1. The undoped SL structures where grown on top of a 300 nm thick undoped GaAs buffer layer on Te-doped (001) GaAs substrates by metal-organic vapor phase epitaxy (MOVPE). We observe the well-known Berreman-polariton effect within the GaAs LO-phonon region. We further observe a strong polariton-like resonance near the coupled longitudinal-optical plasmon-phonon frequency of the Te-doped substrate at 306 cm−1. For analysis of the IRSE data we employ the harmonic oscillator dielectric function model and the Drude model for free-carrier response. The additional resonance feature is explained by pseudo surface polariton (PSP) interface modes between the Te-doped GaAs and the undoped GaAs buffer layer / SL film. We find that the PSP modes are extremely sensitive to free-carrier properties within the SL structures, and we obtain a strong increase in free-carrier concentration within the GaNAs SL sublayers with increasing x from analysis of the IRSE data. We further observe the localized vibrational modes of nitrogen at 470 cm−1 in the GaNxAs1−x SL sublayers with a polar strength that increases linearly with x, and which can be used to monitor the nitrogen concentration in GaNxAs1−x.

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Lateral growth of AlxGa1–xN and GaN on SiC substrates patterned by photo-electrochemical etching

MRS Proceedings ◽

10.1557/proc-743-l1.9 ◽

2002 ◽

Vol 743 ◽

Author(s):

U. Rossów ◽

N. Riedel ◽

F. Hitzel ◽

T. Riedl ◽

A. Hangleiter

Keyword(s):

Growth Rates ◽

Electrochemical Etching ◽

Layered Structures ◽

Lateral Growth ◽

Large Defect ◽

Defect Reduction ◽

Group Iii ◽

Group Iii Nitride ◽

Nitride Layers ◽

Defect Densities

AbstractThe large defect densities in heteroepitaxially grown group-III-nitride layers on sapphire or SiC cannot be tolerated in applications such as lasers. We report here on a defect reduction by overgrowth of patterned n-6H-SiC(0001)surfaces.First, we formed mesa structures in the windows of metal masks and then after removal of the masks layers of AlxGa1–xN and GaN were grown by low-pressure MOVPE under conditions of high lateral growth rates. We demonstrate that layers and layered structures can be grown with smooth surfaces and reduced defect densities.

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Optical phonons and free-carrier effects in MOVPE grown AlxGa1−xN measured by Infrared Ellipsometry

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300000673 ◽

1999 ◽

Vol 4 (1) ◽

Cited By ~ 46

Author(s):

M. Schubert ◽

A. Kasic ◽

T.E. Tiwald ◽

J. Off ◽

B. Kuhn ◽

...

Keyword(s):

Dispersion Model ◽

Free Carrier ◽

Model Parameters ◽

Model Calculations ◽

Group Iii ◽

Infrared Ellipsometry ◽

Mode Behavior ◽

Novel Approach ◽

Back Ground ◽

Group Iii Nitride

We report on the application of infrared spectroscopic ellipsometry (IR-SE) for wavenumbers from 333cm−1 to 1200cm−1 as a novel approach to non-destructive optical characterization of free-carrier and optical phonon properties of group III-nitride heterostructures. Undoped α-GaN, α-AlN, α-AlxGa1−xN (x = 0.17, 0.28, 0.5), and n-type silicon (Si) doped α-GaN layers were grown by metal-organic vapor phase epitaxy (MOVPE) on c-plane sapphire (α-Al2O3). The four-parameter semi-quantum (FPSQ) dielectric lattice-dispersion model and the Drude model for free-carrier response are employed for analysis of the IR-SE data. Model calculations for the ordinary (∈⊥) and extraordinary (∈||) dielectric functions of the heterostructure components provide sensitivity to IR-active phonon frequencies and free-carrier parameters. We observe that the α-AlxGa1−xN layers are unintentionally doped with a back ground free-carrier concentration of 1–4 1018cm−3. The ternary compounds reveal a two-mode behavior in ∈⊥, whereas a one-mode behavior is sufficient to explain the optical response for ∈||. We further provide a precise set of model parameters for calculation of the sapphire infrared dielectric functions which are prerequisites for analysis of infrared spectra of III-nitride heterostructures grown on α-Al2O3.

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Determination of Group III Nitride Film Properties by Reflectance and Spectroscopic Ellipsometry Studies

phys stat sol (a) ◽

10.1002/(sici)1521-396x(200001)177:1<107::aid-pssa107>3.0.co;2-8 ◽

2000 ◽

Vol 177 (1) ◽

pp. 107-115 ◽

Cited By ~ 18

Author(s):

R. Goldhahn ◽

S. Shokhovets ◽

J. Scheiner ◽

G. Gobsch ◽

T.S. Cheng ◽

...

Keyword(s):

Spectroscopic Ellipsometry ◽

Nitride Film ◽

Film Properties ◽

Group Iii ◽

Group Iii Nitride

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In situ measurements of wafer bending curvature during growth of group-III-nitride layers on silicon by molecular beam epitaxy

Journal of Crystal Growth ◽

10.1016/j.jcrysgro.2006.11.126 ◽

2007 ◽

Vol 301-302 ◽

pp. 71-74 ◽

Cited By ~ 16

Author(s):

Y. Cordier ◽

N. Baron ◽

F. Semond ◽

J. Massies ◽

M. Binetti ◽

...

Keyword(s):

Molecular Beam Epitaxy ◽

Molecular Beam ◽

In Situ Measurements ◽

Group Iii ◽

Group Iii Nitride ◽

Nitride Layers

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Properties of InN layers grown by High Pressure CVD

MRS Proceedings ◽

10.1557/proc-0955-i08-04 ◽

2006 ◽

Vol 955 ◽

Author(s):

Mustafa Alevli ◽

Goksel Durkaya ◽

Ronny Kirste ◽

Aruna Weesekara ◽

Unil Perera ◽

...

Keyword(s):

High Pressure ◽

High Speed ◽

Growth Parameters ◽

Free Carrier ◽

Dielectric Constants ◽

High Quality ◽

Group Iii ◽

High Efficient ◽

Nitride Alloys ◽

Group Iii Nitride

ABSTRACTIndium nitride (InN) and indium-rich group III-nitride alloys are promising materials for advanced optoelectronic device applications. Indium-rich alloys, e.g. (Ga1-y-xAlyInx)N will enable the fabrication of high-efficient light emitting diodes tunable in the whole visible spectral region, as well as advanced high speed optoelectronics for optical communication operating. The present limitation in this area is the growth of high quality InN and indium-rich group III-nitride alloys as documented in many controversial reports on the true physical properties of InN. The difficulties arise from the low dissociation temperature of InN that requires an extraordinarily high nitrogen overpressure to stabilize the material up to optimum growth temperatures. We developed a novel “high-pressure chemical vapor deposition” (HPCVD) system, capable to control and analyze the vast different partial pressures of the constituents. Our results show that the chosen HPCVD pathway leads to high-quality single crystalline InN, demonstrating that HPCVD is a viable tool for the growth of indium rich group III nitride alloys. The structural analysis of InN deposited on GaN-sapphire substrate by XRD show single phase InN(0002) peaks with full width half maximum (FWHM) around 400 arcsec. Infrared reflectance spectroscopy is used to analyze the plasmon frequencies, high frequency dielectric constants, the free carrier concentrations and carrier mobilities in these layers. For nominal undoped InN layers, free carrier concentrations in the mid 1019 cm−3 and mobilities around 600 cm−2-V-1-s-1 are observed. Further improvements are expected as the growth parameters are optimized. The explored growth parameters are close to of those employed for GaN growth conditions, which is a major step towards the fabrication of indium rich (Ga1−y−xAlyInx)N alloys and heterostructures.

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