Matthieu Moret

Control of InN quantum dot density using rare gases in metal organic vapor phase epitaxy

Indium nitride (InN) quantum dots have been grown on gallium nitride (GaN) templates with heights of 10 and 20nm. The authors demonstrate that the surface densities of the dots are strongly affected by the nature of the carrier gas used during the growth, which can be used to modulate the surface density. The authors show here that replacing nitrogen by helium leads to a decrease of the dot surface density, while argon induces a strong increase of the density. Although validated for the InN∕GaN system, this approach has a more general scope and can be extended to other material systems.

The determination of the bulk residual doping in indium nitride films using photoluminescence

We extend to any temperature, the sophisticated calculation of the evolution of the 2 K photoluminescence energy of InN proposed by Arnaudov et al. [Phys. Rev. B 69, 115216 (2004)], in view of determining the residual doping of thin films. From the detailed line shape modeling, we extract the full width at half maximum of the photoluminescence line which, in the first order, varies like n0.51 at low temperature. This allows us to propose a handy tool for rapid residual doping evaluation. Last, temperature and inhomogeneous broadening effects are analyzed. Ignoring the latter is shown to lead to an overestimation of the residual doping.

Ammonia: A source of hydrogen dopant for InN layers grown by metal organic vapor phase epitaxy

Thermal annealing of InN layers grown by metal organic vapor phase epitaxy (MOVPE) is investigated in nitrogen atmosphere for temperatures ranging from 400 to 550 °C and for heat treatment times up to 12 h. This treatment results in hydrogen outdiffusion, lowering significantly the residual n-type background doping. This mechanism is shown to be reversible through thermal annealing under ammonia atmosphere, responsible of hydrogen incorporation during growth. These results establish a MOVPE process allowing the obtention of InN samples, which exhibit similar electrical properties than molecular beam epitaxy grown samples: a key issue in view of future industrial production of InN based devices.

Phages recognizing the Indium Nitride semiconductor surface via their peptides

Considerable advances in materials science are expected via the use of selected or designed peptides to recognize material, control their growth, or to assemble them into elaborate novel devices. Identifying specific peptides for a number of technologically useful materials has been the challenge of many research groups in recent years. This can be accomplished by using affinity‐based bio‐panning methods such as phage display technologies. In this work, a combinatorial library including billions of clones of genetically engineered M13 bacteriophage was used to select peptides that could recognize improved indium nitride (InN) semiconductor (SC) material. Several rounds of biopanning were necessary to select the phage with the higher affinity from the low variant library. The DNA of this specific phage was extracted and sequenced to set up the related specific adherent peptide. Atomic force microscopy (AFM) is used to demonstrate the real affinity of a selected phage for the InN surface. Due to the possibility of its functionalization with biomolecules and its important physical properties, InN is a promising candidate for developing affinity‐based optical and electrical biosensors and/or for biomimetic applications. Copyright

Pressure cycling of InN to 20 GPa: In situ transport properties and amorphization

Indium nitride was grown on Al2O3 substrate and characterized by x-ray diffraction, Raman, electrical resistivity, Hall, and magnetoresistance studies. Thermoelectric and electrical properties of free-standing films were measured in situ under high pressure (HP) cycling to 20 GPa, across a phase transformation to a rock-salt-structured lattice. HP-cycling-induced amorphization was established. The thermopower (Seebeck effect) data evidence that both crystalline and amorphous InN kept n-type conductivity to 20 GPa. Pressure effect on the carrier concentration and effective mass is analyzed. Two features that can be related to structural transitions in amorphous InN were found near 11 and 17 GPa.

The epitaxial growth of indium nitride using berlinite (AlPO4) and other piezoelectric crystals of the quartz family as substrates

We report the growth of indium nitride on AlPO4, which is a piezoelectric substrate, by using metal organic vapor phase epitaxy (MOVPE). The substrate we used was the as-grown (011) surface of an AlPO4 crystal grown by hydrothermal synthesis. InN growth occurs as the nonpolar M-plane. The structural, optical, and electrical properties of the epilayer are comparable with those of layers obtained by conventional growth on polar GaN MOVPE templates deposited on C-plane sapphire. We discuss the utilization of other MX–O4 oxides for growing nitrides.

MOCVD Growth of Cubic Gallium Nitride: Effect of V/III Ratio

We have grown cubic GaN on GaAs(001) substrates by MOCVD using a double step process with a buffer deposition at 400 °C. The purpose of the buffer deposited at very low temperature is to prevent GaAs decomposition at growth temperature. We have focused on the effect of the NH3/TEGa molar ratio on the growth of this metastable phase. We have assessed the crystalline quality using X-ray diffraction in the θ–2θ mode, and have used low temperature (2 K) PL for evaluating the optical properties of the GaN films. We found an optimum V/III ratio of 1250 at the growth temperature of 800 °C.

X-Ray Reciprocal space mapping studies of strained GaN/AlGaN quantum wells

In this work, we report on the systematic X-ray reciprocal space mapping of a series of GaN/AlGaN samples, with different Al content and well thickness. For coherently grown samples, we present a calculation which allow us to precisely determine the strain state and Al content in the samples in one diffraction experiment. In our samples, both GaN and AlGaN are strained, and we discuss the effect of these strains on the band structure of GaN, which is probed by low temperature reflectivity and correlates perfectly our x-ray results.

Modeling of Nitride Semiconductor Based Double Heterostructure Tunnel Diodes

Double heterostructure diodes were widely studied in the 80s, based on the use of “classical” III-V materials, i.e. based on (Ga, Al, In, As, P). Negative differential conductivities were predicted in these systems, making them highly interesting for hyperfrequency applications, but experimental results were always far from theoretical predictions, which resulted in a loss of interest for these systems. Recently, there has been a lot of efforts devoted to Nitride semiconductors, based on (Al,Ga,In)N alloys. These materials have been regarded as potential candidates for high frequency, high power applications, since they both exhibit high electron saturation velocities and high thermal and chemical stability. Moreover, although they usually contain a lot of growth defects, device properties were surprisingly good with regards to defect densities. In this work, we have modeled double heterostructure tunnel diodes based on AlGaN/GaN system. The extremely high conduction band offset in these materials, along with the quite low dielectric constants, and built-in electric fields (originating from both the spontaneous and piezoelectric polarization), are extremely favorable parameters, which may renew the interest for such devices in this material system. It will be shown that the built-in electric field leads to a symmetric potential profile under a given external applied bias, which optimizes the transmission coefficient in the structure. We have calculated extremely high peak/valley ratios, which suggests that even mid quality samples could still exhibit interesting device properties.

Optimization of the carbonized buffer layer for the growth of high quality single crystal SiC on Si

Carbonized buffer layers were formed on Si (100) nominally oriented substrates with propane diluted in palladium purified hydrogen in a cold wall vertical reactor. Subsequent SiC layers were grown using silane and propane at atmospheric pressure. The growth temperature was ranging from 1150°C to 1350°C. The layers obtained were characterized by LT photoluminescence, IR reflectivity, X-ray diffraction, micro-Raman on cleaved edges, AFM imaging, and optical microscopy. Drastic influence on the layer surface morphology was evidenced depending on the transition step between the carbonization and the SiC epitaxial growth. As a result, we have developed a carbonization process leading to very high quality 3CSiC films grown at 1250°C.