Liquid Phase Electroepitaxy Research Articles

Raman spectroscopy of lithium niobite (LiNbO2)

Lithium niobite (LiNbO2) single crystals fabricated via liquid phase electro-epitaxy are studied by Raman spectroscopy. We present the Raman spectra of the pristine and chemically delithiated LiNbO2 crystals under ambient conditions. Two characteristic experimental Raman peaks located at 456 cm−1 and 640 cm−1 are assigned to the O E2g and O A1g phonon modes respectively, as determined from first principles-based calculations. Furthermore, by chemically delithiating the crystals it is shown that the spectral changes of the O E2g can be used to capture lithium content variation within the structure.

Orientation-dependent transport properties of Cu3Sn

Cu3Sn, a well-known intermetallic compound with a high melting temperature and thermal stability, has found numerous applications in microelectronics, 3D printing, and catalysis. However, the relationship between the material's thermal conductivity anisotropy and its complex anti-phase boundary superstructure is not well understood. Here, frequency domain thermoreflectance was used to map the thermal conductivity variation across the surface of arc-melted polycrystalline Cu3Sn. Complementary electron backscatter diffraction and transmission electron microscopy revealed the thermal conductivity in the principal a, b, and c orientations to be 57.6, 58.9, and 67.2 W/m-K, respectively. Density functional theory calculations for several Cu3Sn superstructures helped examine thermodynamic stability factors and evaluate the direction-resolved electron transport properties in the relaxation time approximation. The analysis of computed temperature- and composition-dependent free energies suggests metastability of the known long-period Cu3Sn superstructures while the transport calculations indicate a small directional variation in the thermal conductivity. The ∼15% anisotropy measured and computed in this study is well below previously reported experimental values for samples grown by liquid-phase electroepitaxy.

Lateral growth of GaN by liquid phase electroepitaxy using mesa-shaped substrate

GaN microchannel epitaxy (MCE) was performed using a mesa-shaped substrate and liquid phase electroepitaxy. A flat and wide MCE layer was successfully obtained with a rectangular shape, which is formed by ±c-planes on both the top and bottom surfaces. MCE growth proceeded mainly in the lateral direction by the formation of these planes. Cathodoluminescence measurements showed that the laterally grown layers were almost free of dislocations, and that the dislocations in the mesa areas were confined by the vertical sides of the mesas. In the case of inclined sides, the dislocations would be expected to bend and spread into the laterally grown areas.

Selective growth of GaN by liquid phase electroepitaxy using aluminum oxide mask

Aluminum oxide was investigated as a mask material for the selective growth of GaN by liquid phase electroepitaxy in comparison with SiO2, SiN, and W. SiO2 and W masks were dissolved in a solution and many polycrystals were generated on the SiN mask. Therefore, these masks are not suitable for selective growth. On the other hand, aluminum oxide was found durable in the solution, and growth selectivity was also achieved. Then, microchannel epitaxy was conducted using the aluminum mask by liquid phase electroepitaxy. Not only the selective growth but also the lateral growth of c-plane GaN with a width of about 8 µm was successfully achieved using the aluminum oxide mask.

Modulation of Growth Rate by Electric Current in Liquid-Phase Epitaxy of 4H-SiC

The crystallization of 4H-SiC from Si–C solution in liquid-phase electroepitaxy (LPEE) at 1870 and 2050 °C was investigated. The growth of 4H-SiC was enhanced or suppressed by the application of DC with positive or negative polarity, respectively. By the application of AC, the Joule heating effect was separated from the effect of DC on LPEE. We showed that the effect of DC on LPEE consists of a linear electromigration effect and a quadratic Joule heating effect. The results demonstrate that growth rate can be controlled by adjusting not only temperature but also electric current. The variation of growth rate with temperature in LPEE was also examined, and it was shown that the electromigration effect can be controlled independently of the Joule heating effect by increasing the C concentration in the Si–C solution. At higher temperatures, the growth rate in LPEE can be improved without the enhancement of the Joule heating effect.

Epitaxial Cu–Sn bulk crystals grown by electric current

Epitaxial Cu3Sn and Cu6Sn5 grown by liquid-phase electroepitaxy (LPEE) have been demonstrated in this work. X-ray diffraction analysis reveals that LPEE-grown Cu3Sn and Cu6Sn5 grew in particular directions (planes) with respect to the electron flow. LPEE-grown Cu3Sn grew in the 〈020〉 and 〈400〉 directions, and LPEE-grown Cu6Sn5 grew in the 〈204〉 and 〈623¯〉 directions. With the aid of a molecular simulation software tool, we conclude that the particular growth directions represent the low-resistance paths for electron flow. This means that, along those particular directions in the LPEE-grown Cu–Sn compounds, the traveling electrons would be scattered least by the lattice. Thus, as the electromigrating Cu atoms form Cu–Sn compound, the newly forming Cu–Sn unit cells would orientate themselves in those particular growth directions to facilitate electron flow. Then, the well-oriented newly formed Cu–Sn compound unit cells can incorporate the growth of the highly orientated LPEE-grown Cu–Sn compounds. In addition, the anisotropy of a number of properties of LPEE-grown Cu3Sn and Cu6Sn5, i.e. coefficient of thermal expansion, Vickers microhardness and electrical properties (resistivity, carrier mobility and carrier concentration), along the particular orientations were measured and reported.

Plasma-assisted molecular beam epitaxy process combined with a liquid phase electroepitaxy, a novel method for the growth of GaN layers

We have studied a novel approach for the growth of GaN layers, namely plasma-assisted electroepitaxy (PAEE). We have designed and built a new growth chamber which allowed us to combine a plasma-assisted molecular beam epitaxy process with a liquid phase electroepitaxy. We have demonstrated that it is possible to grow continuous GaN layers by PAEE from a liquid Ga melt at growth temperatures as low as ∼650°C, with low nitrogen overpressures of ∼3×10−5Torr.

Control of growth uniformity of III–V bulk crystals grown by contactless liquid phase electroepitaxy

Systematic studies of influence of crucible design on uniformity of growth of bulk III–V crystals by contactless liquid phase electroepitaxy (CLPEE) are reported. CLPEE removes the most important drawback of standard liquid phase electroepitaxy, i.e. limited thickness of crystals being due to superheating of the growing crystals by Joule heat generation. However, the CLPEE method in its simplest version suffers from enhanced growth rate at the center of the crystal, which results from majority of electric current flowing to the center of the electrode and dragging solute species. A number of various designs of growth crucible are examined showing that optimized triple-electrode system is capable to provide perfectly uniform growth rate distribution over a large portion of the surface of the growing crystal. In this way the main obstacle in development of the CLPEE technique is removed allowing application of electroepitaxy to obtain large diameter high crystalline quality single crystals with potentially unlimited thickness.

Plasma-assisted electroepitaxy of GaN layers from the liquid Ga melt

In this current paper we have studied a novel approach for the growth of GaN layers, namely plasma-assisted electroepitaxy (PAEE). In this method, we have combined the advantages of the plasma process for producing high concentrations of active N species in the Ga melt with the advantages of electroepitaxy in transferring the N species from the Ga surface to the growth interface, without spontaneous crystallisation on the surface or within the solution. We have designed and built a new growth chamber which allowed us to combine the plasma-assisted molecular beam epitaxy process with a liquid-phase electroepitaxy system. We have demonstrated that it is possible to grow continuous GaN layers by PAEE from liquid Ga melt at growth temperatures as low as ∼650°C, with low nitrogen overpressures of ∼3×10−5Torr.

Plasma‐assisted electroepitaxy as a novel method for the growth of GaN layers

AbstractIn the current study we have demonstrated the feasibility of a novel approach for the growth of GaN layers, namely plasma‐assisted electroepitaxy (PAEE). In this method, we have combined the advantages of the plasma process for producing high concentrations of active N species in the Ga melt with the advantages of electroepitaxy in transferring the N species from the Ga surface to the growth interface, without spontaneous crystallisation on the surface or within the solution. We have designed and built a new growth chamber which allows us to combine the plasma‐assisted molecular beam epitaxy process with a liquid phase electroepitaxy system. We have demonstrated that it is possible to grow GaN layers by PAEE at growth temperatures as low as ∼650 oC and with low nitrogen overpressures of ∼3×10‐5 Torr. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ni Interdiffusion Coefficient and Activation Energy in Cu6Sn5

Ni diffusion in Cu6Sn5 intermetallic compound was investigated. First, we successfully fabricated preferred-orientation Cu6Sn5 crystal by liquid-phase electroepitaxy (LPEE). Then, Ni/Cu6Sn5 diffusion couples were produced by sputtering from a Ni thin film onto the Cu6Sn5 crystal. Ni/Cu6Sn5 diffusion couples were annealed at different temperatures of 120°C, 160°C, 200°C, 255°C, 290°C, and 320°C for 2 h in a vacuum. The Ni atomic profile across the Ni/Cu6Sn5 interface was obtained by electron spectroscopy for chemical analysis (ESCA). From the Ni atomic profiles, the Matano method was used to evaluate the Ni interdiffusion coefficients (\( \tilde{D}_{\rm{Ni}} \)) in the Cu6Sn5 crystal obtained with different annealing temperatures, which then yields the activation energy for Ni diffusion in the Cu6Sn5 crystal at a particular Ni content. We found that, as Ni diffuses in the ternary Cu6−xNixSn5 compound phase, the activation energy of Ni interdiffusion decreases with the Ni content.

Unlimited Growth of III–V Bulk Crystals by Liquid-Phase Electroepitaxy

A new liquid-phase technique allowing one to grow large-size single crystals in nearly isothermal conditions by application of electric current flow is presented. The technique, denoted as contactless liquid-phase electroepitaxy (CLPEE), removes the most important drawback of standard liquid-phase electroepitaxy (LPEE), i.e., superheating of the growing crystal by Joule heat generation. The CLPEE growth method paves the way to obtain large-diameter high crystalline quality single crystals with potentially unlimited thickness. In an illustration of the method, results of time-dependent simulations of growth of GaAs by current-controlled contactless liquid-phase electroepitaxy (CLPEE) are reported.

Liquid phase electroepitaxy of semiconductors under static magnetic field

The article presents a short review of the growth of single crystal bulk semiconductors by liquid phase electroepitaxy (LPEE) under a static magnetic field. Following a short introduction on early modelling and theoretical studies on LPEE, recent experimental results of the LPEE growth of GaAs/GaInAs single crystals under a static applied magnetic field are discussed. Crystal growth experiments show that the application of a static magnetic field in the LPEE growth of GaAs increases growth rate very significantly. A continuum model that introduces a new electric mobility, i.e., the electromagnetic mobility, allows accurate predictions for both the growth rate and the growth interface shape. A thermodynamic and kinetic interpretation for this electromagnetic mobility is given.

Plasma-assisted electroepitaxy as a method for the growth of GaN layers

In the current study we have demonstrated the feasibility of a novel approach for the growth of the GaN layers namely plasma-assisted electroepitaxy (PAEE). In this method, we have tried to combine advantages of the plasma process for producing high concentrations of active N species in the Ga melt with the advantages of electroepitaxy in transferring the N species from the Ga surface to the growth interface without spontaneous crystallization on the surface or within the solution. We have designed and built a new growth chamber which allows us to combine the Molecular Beam Epitaxy process with a Liquid Phase Electroepitaxy system. We have demonstrated that it is possible to grow GaN layers by PAEE at growth temperatures as low as ∼500 °C and with low nitrogen overpressures of ∼3×10 −5 Torr. We have shown that the combination of the two processes, an N-plasma flux and a DC current, are vital for the successful growth of GaN layers by PAEE. The exact mechanisms, which lead to the growth of GaN by PAEE, still need to be investigated.

Time dependent simulations of the growth of III–V crystals by the liquid phase electroepitaxy

Results of time dependent simulations of growth of bulk binary III–V crystals by current controlled liquid phase electroepitaxy (LPEE) are reported using GaAs as an example. Without any electrical current the LPEE system is isothermal, kept at 1073K, thus no growth occurs. The electric current density of 10A/cm2 leads to ohmic heating of the entire system, Peltier cooling of the Ga–GaAs(seed) interface and electromigration of As species in liquid Ga. Neither Peltier nor Joule effects are considered at the source/solution interface since in the configuration chosen the electric current bypasses the source crystal. The Peltier induced cooling and electromigration of As induce growth of GaAs, originally at the rate of 0.5μm/min. As the growth proceeds the Peltier cooling starts to be compensated by Joule heating inside the crystal grown. Thus, the growth slows down and finally the average growth rate decreases to zero. It is shown that the LPEE growth is strongly time dependent, leading to the change in crystallization front, reflecting the slowest growth rate at the center of the crucible and the fastest close to the crucible wall. The temperature, As concentration convection and electric current distribution are presented showing their influence on the surface morphology of growing GaAs crystal.

Numerical analysis of growth kinetics of bulk III‐V crystals grown by liquid phase electroepitaxy

AbstractResults of time‐dependent simulations of growth of bulk binary III–V crystals by current controlled liquid phase electroepitaxy (LPEE) are presented using GaAs as example. Without any electrical current the LPEE system is isothermal, kept at 1073 K, thus no growth occurs. The electric current density of 10 A/cm2 leads to ohmic heating of the entire system, Peltier cooling of the Ga‐GaAs(seed) interface and electromigration of As species in liquid Ga. Neither Peltier nor Joule effects are considered at the source/solution interface since in the configuration chosen the electric current bypasses the source crystal. The Peltier‐induced cooling and electromigration of As induce growth of GaAs, originally at the rate of 0.5 μm/min. As the growth proceeds, the Peltier cooling is overcompensated by Joule heating, which leads to the reduction of growth rate and finally to standstill. It is shown that the LPEE growth is strongly time dependent, leading to the change of crystallization front, reflecting the fastest growth rate at the center of the crucible and the slowest, close to the crucible wall. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

10.1007/s11455-008-1021-y

A liquid phase epitaxy (LPE) technique for growing indium arsenide (InAs)based narrow-bandgap semiconductor compounds for thermophotovoltaic (TPV) applications has been developed. InAs-based multicomponent solid solutions and InAs/InAsSbP heterostructures with E g = 0.35–0.6 eV are promising materials for TPV converters that operate at an emitter temperature of 1000–2000°C. The sensitivity of new TPV elements is extended toward longer wavelengths (up to 3.8 μm), which ensures effective conversion of low-energy photons. The epitaxial films of quaternary InAsSbP solid solutions were obtained by LPE from a supercooled solution melt and by the liquid phase electroepitaxy technique with controlled doping of a growth solution from a single liquid source of components. The films have homogeneous compositions and highly perfect crystal structures. The values of reverse saturation currents in n-InAs/p-InAsSbP heterostructures are close to theoretical predictions.

X-Ray High-Resolution Diffraction and Transmission Topography Study of InGaAs Grown by Liquid Encapsulated Czochralski Technique

Laser diodes, solar cells, photodetector structures and other optoelectronic applications of InGaAs ternary bulk crystals and layers stimulate constant interest in the improvement of growth methods for this material. Growth of bulk ternary crystals based on III–V compounds with chemical compositions given by formula A 1−xB III x C V is a difficult task due to the thermodynamical properties of their solutions. Most of the techniques to obtain ternary crystals are focused on layer growing on the relevant substrates. Techniques like metalorganic chemical vapor deposition (MOCVD) [1, 2], metalorganic vapor phase epitaxy (MOVPE) [3, 4] and molecular beam epitaxy (MBE) [5, 6] are often used. Growth of quantum wells and quantum wires is also focused on ternary crystals. Some theoretical discussions about bulk growth of ternaries can be found in [7]. Recently rotational Bridgman method [8], liquid phase electroepitaxy [9] and zone growth [10] were used. ∗corresponding author; e-mail: Jerzy.Gronkowski@fuw.edu.pl

InAsSbP/InAs heterostructures for thermophotovoltaic converters: Growth technology and properties

A liquid phase epitaxy (LPE) technique for growing indium arsenide (InAs)based narrow-bandgap semiconductor compounds for thermophotovoltaic (TPV) applications has been developed. InAs-based multicomponent solid solutions and InAs/InAsSbP heterostructures with E g = 0.35–0.6 eV are promising materials for TPV converters that operate at an emitter temperature of 1000–2000°C. The sensitivity of new TPV elements is extended toward longer wavelengths (up to 3.8 μm), which ensures effective conversion of low-energy photons. The epitaxial films of quaternary InAsSbP solid solutions were obtained by LPE from a supercooled solution melt and by the liquid phase electroepitaxy technique with controlled doping of a growth solution from a single liquid source of components. The films have homogeneous compositions and highly perfect crystal structures. The values of reverse saturation currents in n-InAs/p-InAsSbP heterostructures are close to theoretical predictions.

An interpretation for high growth rates in electroepitaxial growth of GaAs under magnetic field

Recent crystal growth experiments of GaAs by liquid phase electroepitaxy (LPEE) showed that the application of a static magnetic field enhances significantly the mass transport mechanism of LPEE, known as electromigration, and the growth rate is proportional linearly to the applied magnetic field intensity and increases with the field intensity level. The exceptionally large increase in electromigration was previously predicted from a global continuum model by introducing a magnetic mobility in the constitutive equations for the Ga–As solution, similar to the well-known electric mobility. In this article we provide a thermodynamic interpretation for the magnetic mobility, and the crystal growth kinetics that predicts the experimentally observed magnetic field increase in crystal growth rate.