The effect of the built-in biaxial stress on the
E
2 and
A
1 (LO) q = 0 phonon modes of wurtzite GaN layers deposited by Metal Organic Vapor Phase Epitaxy on (0 0 0 1) direction on sapphire ...substrates is studied by Raman spectroscopy. Shifts in phonon frequencies are measured, which we correlate to the residual strain fields in the epilayers. Using stress calibration measurements taken from reflectance data, the biaxial pressure coefficients of mode frequencies are determined and used to calculate the corresponding deformation potentials.
We study the influence of defect states (shallow donors and deep acceptors) on the carrier relaxation dynamics of gallium nitride in the picosecond regime for different excitation intensities and ...different lattice temperatures. Time-resolved luminescence, degenerate, and nondegenerate four-wave mixing experiments show a saturation threshold in the blue and yellow spectral region, which is found to disappear for lattice temperatures below 200 K. When analyzing all these results in the frame of a rate-equation model, we give a relaxation scenario for the carriers, the lifetimes of the population of the different states, and identify radiative and nonradiative transitions. After filling defect states by an optical excitation, the ambipolar diffusion coefficient of GaN is measured through degenerate four-wave mixing experiments. A law value of 0.16 cm(2)/s at room temperature is determined, indicating that defect states still influence the diffusion. Nondegenerate four-wave mixing experiments exhibit a competition between an electronical and a thermal contribution to the nonlinear susceptibility in GaN. S0163-1829(99)00340-9.
The most‐common physical properties of the precursor species SiCl4 and GeCl4 in their vapor and liquid phases are compiled from several sources in the literature. General expressions over a large ...range of temperature are proposed either by the use of referenced expressions or by the use of suitable empirical models.
MOVPE growth of zincblende magnesium sulphide Konczewicz, L.; Bigenwald, P.; Cloitre, T. ...
Journal of crystal growth,
02/1996, Volume:
159, Issue:
1-4
Journal Article, Conference Proceeding
Peer reviewed
The successful growth of MgS epitaxial layers with the MOVPE technique is reported. The samples were grown on GaAs substrates in a classical horizontal reactor, using bis(methylcyclopentadienyl) ...magnesium and H2S as precursors. The zincblende structure of MgS layers is evidenced by careful X-ray diffraction analysis. The lattice constant is found to be about 5.66 Å. The influence of the growth temperature on the morphology and quality of the layers is studied in detail.
MOVPE growth and characterization of AlxGa1-xN RUFFENACH-CLUR, S; BRIOT, O; ROUVIERE, J. L ...
Materials science & engineering. B, Solid-state materials for advanced technology,
12/1997, Volume:
50, Issue:
1-3
Conference Proceeding, Journal Article
Peer reviewed
AlGaN is an important material in the design of nitride devices. However, little is known concerning its growth with high Al contents. We have studied the growth of AlxGa1-xN epilayers on c-face ...sapphire by low pressure MOVPE (76 Torr), using triethylgallium, trimethylaluminum and ammonia as precursors. The solid versus gas phase composition relationship was determined experimentally and was fitted using a kinetic model. Then the structural properties of the layers (x = 0-1) were studied, using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. We demonstrate that at high Al content, the buffer layer defects are replicated into the AlGaN layer. (C) 1997 Elsevier Science S.A.
Optimization of the MOVPE growth of GaN on sapphire Briot, O.; Alexis, J.P.; Tchounkeu, M. ...
Materials science & engineering. B, Solid-state materials for advanced technology,
1997, 1997-1-00, Volume:
43, Issue:
1
Journal Article
Peer reviewed
The low pressure MOVPE growth process of GaN deposited onto GaN buffer layers on sapphire substrates is studied in detail. The relevant growth parameters are identified, and their influences are ...studied. These include the influence of the sapphire nitridation, the growth of the GaN buffer layer and its subsequent thermal treatment, and the growth parameters of the GaN epilayer (growth temperature, precursor flow rates, V/III ratio, etc.). Low temperature photoluminescence was mainly used to investigate the layer quality and, as a result of this optimization study, we have been able to reproducibly grow layers which have a 2 K photoluminescence dominated by the free exciton.
Specific space charge zones on the substrate side of (100) ZnSe/GaAs interfaces, corresponding to strong band bending, were investigated within the vibrational and optical energy ranges by using ...combined Raman scattering and photoreflectance. While the conventional Raman set-up provides surprisingly an unperturbed Raman response, micro-Raman measurements performed at the near-interface on a cleaved (110) face show the activation of a theoretically forbidden LO
GaAs mode, attributed to the expected electric-field-induced Raman scattering (EFIRS). Besides, the observation of Franz–Keldysch oscillations above the fundamental gap of GaAs by photoreflectance provides experimental evidence of another nature for strong interfacial static electric fields and provides an estimation of their average value. These are in good agreement with the activation of EFIRS effects.
In this paper we present measurements of light amplification in optically pumped ZnCdSe graded refraction index separate confinement heterostructures (GRINSCH). In several differently designed ...samples we observe the presence of two gain mechanisms, which involve localized excitons and exciton–exciton inelastic scattering processes, respectively. The influence of the GRINSCH structure on gain is discussed with respect to light guiding variations due to sample design. A numerical simulation is used to investigate the phenomenon of gain quenching with decreasing barrier width.
