Pierre Gibart

Bio: Pierre Gibart is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Metalorganic vapour phase epitaxy & Epitaxy. The author has an hindex of 45, co-authored 332 publications receiving 8248 citations. Previous affiliations of Pierre Gibart include Saint-Gobain.

Temperature quenching of photoluminescence intensities in undoped and doped gan

Abstract: This work discusses the temperature behavior of the various photoluminescence (PL) transitions observed in undoped, n- and p-doped GaN in the 9-300 K range. Samples grown using different techniques have been assessed. When possible, simple rate equations are used to describe the quenching of the transitions observed, in order to get a better insight on the mechanism involved. In undoped GaN, the temperature dependence of band edge excitonic lines is well described by assuming that the A exciton population is the leading term in the 50-300 K range. The activation energy for free exciton luminescence quenching is of the order of the A rydberg, suggesting that free hole release leads to nonradiative recombination. In slightly p-doped samples, the luminescence is dominated by acceptor related transitions, whose intensity is shown to be governed by free hole release. For high Mg doping, the luminescence at room temperature is dominated by blue PL in the 2.8-2.9 eV range, whose quenching activation energy is in the 60-80 meV range. We also discuss the temperature dependence of PL transitions near 3.4 eV, related to extended structural defects. (C) 1999 American Institute of Physics. [S0021-8979(99)05619-4].

Stress control in GaN grown on silicon (111) by metalorganic vapor phase epitaxy

Abstract: The strain in GaN epitaxial layers grown on silicon (111) substrates by metalorganic vapor phase epitaxy has been investigated. The insertion of AlN/GaN superlattices was found to decrease the stress sufficiently for avoiding crack formation in an overgrown thick (2.5 μm) GaN layer. X-ray diffraction and photoluminescence measurements are used to determine the effect of these AlN/GaN superlattices on the strain in the subsequent GaN layers. A reduction of threading dislocation density is also observed by transmission electron microscopy and atomic force microscopy when such superlattices are used. Strong band edge photoluminescence of GaN on Si(111) was observed with a full width at half maximum of the bound exciton line as low as 6 meV at 10 K. The 500 arcsec linewidth on the (002) x-ray rocking curve also attests the high crystalline quality of GaN on Si (111), when using these AlN/GaN superlattices.

Epitaxial Lateral Overgrowth of GaN

Abstract: Since there is no GaN bulk single crystal available, the whole technological development of GaN based devices relies on heteroepitaxy. Numerous defects are generated in the heteroepitaxy of GaN on sapphire or 6H-SiC, mainly threading dislocations (TDs). Three types of TDs are currently observed, a type (with Burgers vector 1/3〈〉); c type (with 〈0001〉) and mixed a+c (1/3〈〉). The Epitaxial Lateral Overgrowth (ELO) technology produces high quality GaN with TD densities in the mid 106 cm—2, linewidth of the low-temperature photoluminescence (PL) near-bandgap recombination peaks <1 meV and deep electron traps reduced below 1014 cm—3 (compared to mid 1015 cm—3 in standard GaN). Numerous modifications of the ELO process have been proposed in order either to avoid technological steps (mask-less ELO) or to improve it (pendeo-epitaxy). Basically developed on either sapphire or 6H-SiC, the ELO technology is also achievable on (111)Si or (111)3C-SiC/Si provided that an appropriate buffer layer is grown to avoid cracks. More sophisticated technologies have been implemented to further increase the useable part of the ELO GaN surface (two technological steps, three-step ELO). Unfortunately, in-depth understanding of the basic ELO process is still missing, i.e. of the growth anisotropy and bending of dislocations.

III nitrides and UV detection

Abstract: III nitrides have become the most exciting challenge in optoelectronic materials in the last decade. Their intrinsic properties and an intense technological effort have made possible the fabrication of reliable and versatile detectors for short wavelengths. In this work, materials and devices issues are considered to provide a full picture of the advances in nitride UV photodetection. First, basic structures like photoconductors, Schottky, p-i-n and metal-semiconductor-metal photodiodes and phototransistors are compared, with emphasis on their specific properties and performance limitations. The efforts in the design and fabrication of more advanced detectors, in the search for higher quantum efficiency, contrast, signal-to-noise or speed operation, are reviewed afterwards. Metal-insulator-semiconductor diodes, avalanche photodetectors and GaN array detectors for UV imaging are also described. Further device optimization is linked with present materials issues, mainly due to the nitride quality, which is a direct result of the substrate used. The influence of substrates and dislocations on detector behaviour is discussed in detail. As an example of AlGaN photodetector applications, monitoring of the solar UV-B radiation to prevent erythema and skin cancer is presented.

High-performance GaN p-n junction photodetectors for solar ultraviolet applications

Abstract: The fabrication and characterization of ultraviolet photodetectors based on GaN p-n junctions is reported. The devices are grown by metalorganic vapour phase epitaxy on basal-plane sapphire substrates. These detectors are visible-blind with a sharp wavelength cut-off at 360 nm. The photocurrent is linear with incident power from up to , with a responsivity of at 360 nm. The device time response is dominated by the effective resistance-capacitance time constant, and a 105 ns response is estimated for very low load resistances. A comparison with the response of GaN photoconductor detectors is also presented. The application of these high-performance photodetectors for solar ultraviolet monitoring is described.

Band parameters for III–V compound semiconductors and their alloys

Abstract: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

First-principles calculations for defects and impurities: Applications to III-nitrides

Abstract: First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be a...

Diode Lasers and Photonic Integrated Circuits

Abstract: Ingredients. A Phenomenological Approach to Diode Lasers. Mirrors and Resonators for Diode Lasers. Gain and Current Relations. Dynamic Effects. Perturbation and Coupled--Mode Theory. Dielectric Waveguides. Photonic Integrated Circuits. Appendices. Index.

Band parameters for nitrogen-containing semiconductors

Abstract: We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Luminescence properties of defects in GaN

Abstract: Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The p...