Epitaxial rare earth oxide and nitride buffers for GaN growth on Si

Dargis, Rytis; Smith, Robin S.; Arkun, F. Erdem; Clark, Andrew

doi:10.1002/pssc.201300426

Cited by 8 publications

(5 citation statements)

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“…The epitaxy of GaN on Si is challenging because of Ga meltback etching of Si due to eutectic Ga-Si reactions occurring even at temperatures close to the Ga melting point of 29.8 °C (13)(14), high dislocation density (>10 8-10 cm -2 ) in the epilayer resulting from the large mismatch (-16.9%) in lateral lattice constant between GaN (a GaN = 3.189 Å) and Si (a Si(111) = 3.84 Å), and significant tensile thermal stress developing during cool-down resulting in concave bending of the Si wafer and cracks in the GaN epilayers due to the large difference (~54%) in thermal expansion coefficient (CTE) between GaN (CTE GaN = 5.59x10 -6 K -1 ) and Si (CTE Si = 2.59x10 -6 K -1 ). To avoid Ga meltback etching, other materials have been used as nucleation or transition layers to isolate GaN from Si, such as AlN (15)(16)(17)(18)(19)(20)(21), SiC (22)(23)(24), HfN (25), ZnO (26), Al 2 O 3 (27) or rare earth oxides or nitrides (28).…”

Section: Introductionmentioning

confidence: 99%

(Invited) Epitaxial III-Nitride Film Growth in a Single Wafer Rotating Disk MOCVD Reactor

Papasouliotis

Balakrishnan

et al. 2015

ECS Trans.

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We are reporting on the epitaxial growth of Al/Ga/N films on 200 mm Si substrates carried out in Veeco's Propel rotating disk, single wafer, vertical MOCVD reactor. The Turbodisc reactor is designed for uniform alkyl and hydride flow distribution, and temperature profile, resulting in uniform and concentrically symmetric epilayer thickness and chemical composition. Results are presented on film stress and wafer curvature control facilitated by adjusting the thickness and growth conditions of individual layers in AlN/GaN superlattices. The growth of highly resistive, intrinsically carbon-doped GaN layers is studied, and the influence of growth conditions, growth temperature, pressure, and V/III ratio, on carbon incorporation rate, crystal quality, and surface morphology will be discussed in this paper. Carbon incorporation is enhanced at lower growth temperature, lower pressure, and lower V/III ratios; we have obtained concentrations as high as 3E19/cm 3 at a growth pressure of 35 Torr and growth temperature of 960 °C.

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Section: Introductionmentioning

confidence: 99%

(Invited) Epitaxial III-Nitride Film Growth in a Single Wafer Rotating Disk MOCVD Reactor

Papasouliotis

Balakrishnan

et al. 2015

ECS Trans.

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“…Recent advances in the fabrication of rare-earth oxide/silicon distributed Bragg reflectors (DBR) have opened up their potential applications in III-N-based light-emitting devices as reflecting substrates [5]. These investigations have demonstrated the excellent chemical and structural stability of these reflectors in typical III-N molecular beam epitaxy (MBE) process conditions [3,6]. The good thermal stability of erbium oxide/silicon structures at high temperatures has also been confirmed.…”

Section: Introductionmentioning

confidence: 87%

GaN growth on Si with rare-earth oxide distributed Bragg reflector structures

Grinys

Dargis²,

Kalpakovaite

et al. 2015

Journal of Crystal Growth

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“…More recently, the REN series has regained interest with advances in film growth and characterisation. Modern thin-film growth techniques that have been applied to the rare-earth nitrides include molecular beam epitaxy, sputter deposition, and pulsed laser deposition [24][25][26][27][28][29]. These high quality samples are prepared in ultra-high vacuum, permitting very low impurity concentrations and high surface quality.…”

Section: Historical Overviewmentioning

confidence: 99%

“…However, diagonal resistance pathways across the junction can still contribute to the measured resistance (this is illustrated in Figure 3.17). The resistance pathways will change as a function of temperature due to the competition between the metallic resistance (which decreases with decreasing temperature) and the semiconducting GdN (which increases with decreasing temperature) 28 .…”

Section: Junction Contact Resistance Effectsmentioning

confidence: 99%

“…In this case there is both a horizontal component from the contacts along with the vertical component which is trying to be measured. A more detailed treatment of the voltage profile in these cross-contact junctions is included in Appendix D. 28 Pomeroy and Grube solve this problem using finite element modelling in the case where the series resistance of the contacts is larger than the device resistance [76]. They show that it is possible to correct for the anomalous resistance contributions due to these contact effects.…”

Section: Junction Contact Resistance Effectsmentioning

confidence: 99%

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Device Applications of Rare-Earth Nitrides

Warring¹

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<p>In this thesis the properties of thin film spintronic devices are investigated. These devices incorporate rare-earth nitrides as the active elements in a geometry with vertical transport perpendicular to the layers. Many rare-earth nitrides are ferromagnetic semiconductors with a rich range of magnetic properties arising from their 4-f magnetic moments. These magnetic moments contain both spin and orbital contributions, in contrast to the quenched, spin-based magnetism frequently exploited in spintronic devices based on transition metals. Magnetic tunnel junctions are demonstrated with the ferromagnetic electrodes made from the intrinsic ferromagnetic semiconductor GdN surrounding GaN and AlN barriers. Fitting of the current-voltage characteristics of a GdN/GaN/GdN device determines a barrier height of 1.5 eV at room temperature. This puts the GdN Fermi level close to the GaN mid-gap, consistent with recent theoretical predictions of the band alignment at the GdN/GaN interface [Kagawa et al., Phys. Rev. Applied 2, 054009 (2014)]. This barrier height is found to scale with the band gap of the group-III nitride barrier, being approximately twice as large for AlN barriers. It was observed that the barrier height reduces as the AlN barrier thickness increases, signalling the formation of Schottky barriers at the interface. These polycrystalline junctions exhibit a tunnel magnetoresistance of a few percent but do not show clear signs of homogeneous switching. The transport properties of the GdN/GaN/GdN junctions are heavily influenced by the electronic structure of the semiconducting GdN layers, making junctions based on rare-earth nitrides promising candidates for further investigation. A fully semiconductor-based magnetic tunnel junction that uses spin-orbit coupled materials made of intrinsic ferromagnetic semiconductors is then presented. Unlike more common approaches, one of the electrodes consists of a near-zero magnetic moment ferromagnetic semiconductor, samarium nitride, with the other electrode comprised of the more conventional ferromagnetic semiconductor gadolinium nitride. Fabricated tunnel junctions exhibit magnetoresistances as high as 200%, implying strong spin polarisation in both electrodes. In contrast to conventional tunnel junctions, the resistance is largest at high fields, a direct result of the orbital-dominant magnetisation in samarium nitride that requires the spin in this electrode aligns opposite to that in the gadolinium nitride when the magnetisation is saturated. The magnetoresistance at intermediate fields is controlled by the formation of a twisted magnetisation phase in the samarium nitride, a direct result of the orbital-dominant ferromagnetism. Thus, new functionality can be brought to magnetic tunnel junctions by use of novel electrode materials, in contrast to the usual focus on tuning the barrier properties. Finally, highly resistive GdN films intentionally doped with Mg are demonstrated. These films are found to have increased resistivities and decreased carrier concentrations, with no observed degradation in crystal quality as compared with undoped films. An increase of the Curie temperature in conductive films is observed which is consistent with the existence of magnetic polarons centred on nitrogen vacancies. The prospect of doping rare-earth nitride films in this manner promises greater control of the material properties and future device applications.</p>

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Epitaxial rare earth oxide and nitride buffers for GaN growth on Si

Cited by 8 publications

References 4 publications

(Invited) Epitaxial III-Nitride Film Growth in a Single Wafer Rotating Disk MOCVD Reactor

(Invited) Epitaxial III-Nitride Film Growth in a Single Wafer Rotating Disk MOCVD Reactor

GaN growth on Si with rare-earth oxide distributed Bragg reflector structures

Device Applications of Rare-Earth Nitrides

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