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Last name: CHENOT
First name: S.
International audience
Any arbitrary state of polarization of a light beam can be decomposed into a linear superposition of two orthogonal direction of the oscillations, each of which has a specific amplitude of the electric field. The dispersive nature of diffractive and refractive optical components generally affects these amplitudes significantly over a small...
The use of tunnel junctions (TJs) is a potential solution in blue LEDs to poor p-contacts, replacing it by another n-contact. TJs are even more advantageous for UV emitting structures, which suffer from the considerably low injection efficiency in high Al concentration UV LEDs. In this work we report our work on Ge n-doped GaN and AlGaN TJs...
In this work, a series of AlGaN/GaN high electron mobility transistors (HEMTs) have been grown on patterned (Al)GaN-on-Si seed layers by metalorganic chemical vapor deposition (MOCVD) to study the effect of the (Al)GaN buffer thickness and its aluminum content on the vertical breakdown voltage. The atomic force microscopy (AFM) analysis...
We report magnetotransport measurements performed on AlGaN/GaN devices with different buffer layers. Standard samples with a 1 μm thick GaN buffer show a linear Hall resistance and an almost constant magnetoresistance, as expected from a single two-dimensional electron gas (2DEG) at the AlGaN/GaN interface. Other samples, with an Al x Ga1– x N...
International audience
We present capacitance-voltage [C(V)] measurements of self-assembled wurtzite-GaN quantum dots (QDs). The QDs are embedded in a charge-tunable diode structure and were grown by molecular beam epitaxy in the Stranski-Krastanov growth method. The internal electric fields present in GaN and its alloys together with its wide bandgap make this...
International audience
We have grown graphene on SiC(0001) using propane-hydrogen CVD. In this work, we present the effects of growth pressure and temperature on structural and electrical properties. Structural characterizations evidence the formation of graphene with in-plane rotational disorder, except for low growth pressure and high growth temperature which lead...
The present work is proposing a comparative analysis of the graphitization, achieved by argon-propane assisted chemical vapor deposition, of 6H-SiC(0001) bulk substrates and 3C-SiC heteroepilayers deposited on (111) and (100) silicon. We have investigated the influence of the experimental parameters of the graphitization (pressure, propane flow...
AlGaN based light emitting diodes (LEDs) will play a key role for the development of applications in the ultra-violet (UV). In the UVB region (280–320 nm), phototherapy and plant lighting are among the targeted uses. However, UVB LED performances still need to be improved to reach commercial markets. In particular, the design and the...
Due to giant built-in electric fields excitons in wide GaN/(Al,Ga)N quantum wells (QWs) are spatially indirect iven in the abscence of any external electric bias and posess microsecond lifetimes, large dipole moment in growth direction, and tens of microns diffusion lengths [Fedichkin2016]. This make them potentially interesting for excitonic...
The Mott transition from a dipolar excitonic liquid to an electron-hole plasma is demonstrated in a wide GaN/(Al,Ga)N quantum well at $T=7$K by means of spatially-resolved magneto-photoluminescence spectroscopy. Increasing optical excitation density we drive the system from the excitonic state, characterized by a diamagnetic behavior and thus a...
A giant built-in electric field in the growth direction makes excitons in wide GaN/(Al, Ga)N quantum wells spatially indirect even in the absence of any external bias. Significant densities of indirect excitons can accumulate in electrostatic traps imprinted in the quantum well plane by a thin metal layer deposited on top of the...
International audience
International audience
A new substrate material, alumina-rich spinel, with better thermal and lattice match to GaN than sapphire, has been developed for growing high-quality GaN-based light-emitting diodes (LEDs). As 1:3 spinel (1 MgO for 3 Al2O3), MgAl6O10, is chemically close to sapphire, Al2O3, we successfully replicated on (1 1 1)-oriented spinel wafers the GaN...
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The stress distribution on crack free thick continuous GaN film (12 mu m) grown by Metal organic chemical vapour deposition (MOCVD) on the arrays of different sizes of the patterned silicon substrate is investigated by micro-Raman (mu Raman) spectroscopy. On the largest crack free mesa (400 mu m) both mu-photoluminescence (mu PL) at low...
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Excitons hosted by GaN/(Al,Ga)N quantum wells (QWs) are spatially indirect due to the giant built-in electricfield that separates electrons and holes along the growth direction. This electric field, and thus exciton energy,can be reduced by depositing metallic layers on the sample surface. Using spatially resolved microphotolu-minescence...