Chloride Vapor Phase Epitaxy Research Articles

Defect structure of α-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- film grown on a m-face sapphire substrate, according to transmission electron microscopy investigation

The results of a study by transmission electron microscopy of the structural state of α-Ga2O3 film with a thickness of about 1 micron, grown on the prismatic m-face sapphire by the method of chloride vapor phase epitaxy, are presented. The influence of the substrate orientation on the formation of the dislocation structure is discussed. Threading dislocations, including those with the Burgers vector 1/3< 1120 >, and dislocation half-loops are revealed. The inclined propagation of dislocations and the formation of dislocation half-loops result in the reduction of the threading dislocation density near the surface.. Keywords: dislocations, gallium oxide, TEM.

Дефектная структура пленки α-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-, выращенной на m-грани подложки сапфира, по данным просвечивающей электронной микроскопии

The results of a study by transmission electron microscopy of the structural state of α-Ga2O3 film with a thickness of about 1 micron, grown on the prismatic m-face sapphire by the method of chloride vapor phase epitaxy, are presented. The influence of the substrate orientation on the formation of the dislocation structure is discussed. Threading dislocations, including those with the Burgers vector 1/3<11-20> , and dislocation half-loops are revealed. The inclined propagation of dislocations and the formation of dislocation half-loops result in the reduction of the threading dislocation density near the surface.

Электропроводящие и фотоэлектрические свойства гетероструктур на основе оксидов галлия и хрома со структурой корунда

α-Ga2O3/α-Cr2O3 heterostructures with a corundum structure were obtained by chloride vapor phase epitaxy and magnetron sputtering. The structural, electrical conductive and photoelectrical properties of the obtained samples were studied. It was established that the α-Ga2O3/α-Cr2O3 heterostructures exhibits weak rectifying properties and in comparison with α-Ga2O3 films has a higher response speed when exposed to ultraviolet radiation.

Electrical conductive and photoelectrical properties of heterostructures based on gallium and chromium oxides with corundum structure

α-Ga2O3/α-Cr2O3 heterostructures with a corundum structure were obtained by chloride vapor phase epitaxy and magnetron sputtering. The structural, electrical conductive and photoelectrical properties of the obtained samples were studied. It was established that the α-Ga2O3/α-Cr2O3 heterostructures exhibits weak rectifying properties and in comparison with α-Ga2O3 films has a higher response speed when exposed to ultraviolet radiation Keywords: Gallium oxide, chromium oxide, corundum, anisotypic heterostructures

Газочувствительные свойства пленок твердого раствора In-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=--Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

The effect of the gaseous medium composition on the electrically conductive properties of In2O3-Ga2O3 films obtained by chloride vapor phase epitaxy has been studied. In the temperature range of 100-550ºC the In2O3 -Ga2O3 films exhibit high sensitivity to H2, NH3 and CO possessing high-speed performance and low-base-resistance. A qualitative mechanism for the sensitivity of In2O3-Ga2O3 films to gases is proposed.

HVPE fabrication of GaN sub-micro pillars on preliminarily treated Si(001) substrate

The work reports on the chloride vapour phase epitaxy growth of a GaN film on the preliminarily treated silicon substrates of Si(001) with a 3° miscut to (011) through the buffer layer of AlN. It was demonstrated that the use of the proposed technology resulted in the formation of a transition sub-layer in the Si substrate with the thickness of ~170–200 nm, and subsequent growth on this layer led to the formation of pillar-like GaN grains with a lateral size of ~500 nm involving the thin interlayer of the AlN phase between the pillars. The epitaxial GaN film was characterised by the low value of the residual stresses calculated using the data of XRD, Raman, and PL measurements. This idea was supported by the intense photoluminescence and the short life time of the photons in the epitaxial layer. The obtained data will be utilised as an important material for the understanding of the basic foundations in the physics of GaN/AlN/Si nano-heterostructures, thus facilitating their potential applications in optoelectronics.

Влияние влажности окружающей среды на электрическую проводимость полиморфных Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=--структур

The effect of ambient humidity on the electrical conductive properties of α-Ga2O3 and α-Ga2O3/ε-Ga2O3 structures has been studied. Polymorphic Ga2O3 epitaxial layers were deposited by chloride vapor phase epitaxy on sapphire substrates. Pt and Pt/Ti were used as contacts. It was found that the Pt/α-Ga2O3/Pt and Pt/Ti/α-Ga2O3/ε-Ga2O3/Ti/Pt structures exhibit a high sensitivity of the current – voltage characteristics (I–V characteristics) to atmospheric humidity in the temperature range 25–100 °C. It was found that the effect of water vapor on the I–V characteristics of the structures is reversible and the most significant changes in the current in the samples are observed at a relative humidity RH ≥ 60%. With increasing temperature the effect of atmospheric humidity on the I–V characteristics decreases and disappears at T > 100 °C. The experimental results obtained are explained in terms of the Grottguss mechanism.

Влияние ультрафиолетового излучения и электрического поля на проводимость структур на основе alpha- и ε-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

The influence of ultraviolet radiation and a strong electric field on the current-voltage characteristic of resistive structures based on polymorphic films of gallium oxide is studied. Both types of Ga2O3 films were obtained by the method of chloride vapor-phase epitaxy on smooth and structured sapphire substrates with orientation (0001). In the same process α-Ga2O3 films were deposited on smooth substrates, and gallium oxide films, with regular structures perpendicular to the substrate, containing alternating regions of the α- and ε-phases were deposited on patterned substrate. It’s was observed, that radiation with λ = 254 nm and strong electric transfer structures from a state with low resistance to a state with high resistance. The response time to UV radiation is 5 seconds, and the recovery time less than 1 s.

Свойства резистивных структур на основе полиморфных фаз оксида галлия

The influence of UV radiation and a strong electric field on the I–V characteristics of resistive structures based on polymorphic films of gallium oxide (Ga2O3) is considered. Ga2O3 films were deposited by the method of chloride vapor-phase epitaxy (HVPE) on smooth and structured sapphire substrates with a baseline (0001) orientation. α-Ga2O3 films were produced on smooth substrates, and deposition on patterned sapphire substrates templates produced a mixed structure containing both α-Ga2O3 and ε-Ga2O3. The switching effect was observed in metal / Ga2O3 / metal structures based on two-phase films. Structures pass from a low-resistance (LR) state to a high-resistance (HR) state when exposed to a strong electric field and radiation with λ = 254 nm.

Growing III–V Semiconductor Heterostructures on SiC/Si Substrates

A three-layer heterostructure consisting of AlN (∼0.72 μm thick), AlGaN (∼ 1.82 μm thick), and GaN (∼2.2 μm thick) layers has been grown by hydride–chloride vapor phase epitaxy (HVPE) method on a Si substrate with a SiC buffer nanolayer. The heterostructure was studied using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and other techniques. The results showed that SiC/Si substrates can be used for growing films of III–V semiconductor compounds by HVPE at a high rate (~66 μm/h) free of cracks and with small residual elastic stresses (~160 MPa).

Thick α-Ga2O3 Layers on Sapphire Substrates Grown by Halide Epitaxy

This work reports on the epitaxial-film growth and characterization of a new wide-gap semiconductor α-Ga2O3. Layers are deposited by chloride vapor phase epitaxy on sapphire substrates with a basal orientation. The thickness of the layers of the investigated samples is from 0.5 μm to a value of 10 μm, the latter being record-breaking for today. The structural and optical properties of the obtained samples are studied. It is shown that all samples are structurally uniform, single phase, and have an R $$\bar {3}$$ c corundum-like structure similar to that of the sapphire used as the substrate. It is shown that the full-width at half-maximum of the rocking curves for the (0006) reflection of α-Ga2O3 changes with the layer thickness and approaches 240 arcsec for the thickest layers. Both thin and thick layers are transparent in the visible and UV (ultraviolet) spectral range up to an absorption edge at 5.2 eV.

Synthesis of Hexagonal AlN and GaN Layers on a Si(100) Substrate by Chloride Vapor-Phase Epitaxy

Synthesis of Hexagonal AlN and GaN Layers on a Si(100) Substrate by Chloride Vapor-Phase Epitaxy

Синтез гексагональных слоев AlN и GaN на Si(100)-подложке методом хлоридной газофазной эпитаксии

AbstractSynthesis of AlN and GaN layers on a Si(100) substrate by chloride vapor-phase epitaxy has been considered. The process includes sulfidizing of the silicon surface, nucleation and growth of an AlN layer, and then formation of a GaN/AlN structure. It has been found that in the case of a (100)Si substrate, GaN nucleates on buffer AlN layers that may have two crystallographic orientations in contrast to a Si(111) substrate, on which a buffer layer may have only one orientation. It has been shown that the treatment of the Si(100) substrate in an aqueous solution of (NH_4)_2S decreases the FWHM of the rocking curve for GaN(0002) by a factor of 1.5.

Asymmetry of the Defect Structure of Semipolar GaN Grown on Si(001)

The defect structure of a thick (~15 μm) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.

Studying the Pyroelectric Effect in AlN Epilayers

We have studied the pyroelectric effect in 6- to 12-μm-thick AlN epilayers grown by hydride–chloride vapor phase epitaxy (HVPE) on 4H-SiC substrates. The pyroelectric current was generated by means of dynamic laser action. Evolution of the temperature fields was monitored by direct measurements of the surface temperature with allowance for the specific thermal heterogeneity of the AlN/SiC system. In combination with the results of pyroelectric current measurements, these data allowed the pyrocoefficient of the AlN/SiC structure to be estimated at p ≈ 3.0 μC/(m2 K). Pyroelectric figures of merit of the given structure are calculated that can be used for the comparison of pyroelectric materials intended for the creation of IR radiation detectors.

Исследование пироэффекта в AlN-эпитаксиальных слоях

AbstractWe have studied the pyroelectric effect in 6- to 12-μm-thick AlN epilayers grown by hydride–chloride vapor phase epitaxy (HVPE) on 4H-SiC substrates. The pyroelectric current was generated by means of dynamic laser action. Evolution of the temperature fields was monitored by direct measurements of the surface temperature with allowance for the specific thermal heterogeneity of the AlN/SiC system. In combination with the results of pyroelectric current measurements, these data allowed the pyrocoefficient of the AlN/SiC structure to be estimated at p ≈ 3.0 μC/(m^2 K). Pyroelectric figures of merit of the given structure are calculated that can be used for the comparison of pyroelectric materials intended for the creation of IR radiation detectors.

Асимметрия дефектной структуры полуполярного GaN, выращенного на Si(001)

AbstractThe defect structure of a thick (~15 μm) semipolar gallium nitride (GaN) layer grown by hydride–chloride vapor phase epitaxy on a Si(001) substrate with buffer layers has been studied by transmission electron microscopy. The asymmetry of the defect structure of GaN epilayer has been revealed and analyzed. The influence of this asymmetry on the rate of decrease in the density of threading dislocations in the growing epitaxial layer is discussed.

Etching and ellipsometry studies on CL-VPE grown GaN epilayer

Abstract The surface morphological characteristics of wet chemical etched GaN layers grown at different temperatures on (0 0 0 1) sapphire substrates by Chloride-Vapor Phase Epitaxy (Cl-VPE) have been studied using optical microscope. Significant surface morphology changes have been observed in correlation to the growth temperature and etching time. Also optical properties of the as grown and high-energy silicon (Si) ion irradiated gallium nitride (GaN) epilayers were studied using monochromatic ellipsometry. The effect of ion fluences on the refractive index of the GaN has been investigated and it has been found to decrease with an increase of ion fluence. This decrease is attributed to irradiation-induced defects and polycrystallization which plays an important role in determining the optical properties of silicon (Si) ion irradiated GaN layers.

Epitaxial gallium oxide on a SiC/Si substrate

Well-textured gallium oxide β-Ga2O3 layers with a thickness of ~1 μm and a close to epitaxial layer structure were grown by the method of chloride vapor phase epitaxy on Si(111) wafers with a nano-SiC buffer layer. In order to improve the growth, a high-quality silicon carbide buffer layer ~100 nm thick was preliminarily synthesized by the substitution of atoms on the silicon surface. The β-Ga2O3 films were thoroughly investigated using reflection high-energy electron diffraction, ellipsometry, X-ray diffraction, scanning electron microscopy, and micro-Raman spectroscopy. The investigations revealed that the films are textured with a close to epitaxial structure and consist of a pure β-phase Ga2O3 with the (\(\overline 2 01\)) orientation. The dependence of the dielectric constant of epitaxial β-Ga2O3 on the photon energy ranging from 0.7 to 6.5 eV in the isotropic approximation was measured.

TEM study of defect structure of GaN epitaxial films grown on GaN/Al2O3 substrates with buried column pattern

A TEM study of defect structure of GaN films grown by chloride vapor-phase epitaxy (HVPE) on GaN/Al2O3 substrates was performed. The substrates were fabricated by metal-organic chemical vapor deposition overgrowth of templates with buried column pattern. The results of TEM study showed that the character of the defect structure of HVPE-grown films was determined by the configuration of the column pattern in the substrate. By choosing the proper pattern, the reduction in the density of threading dislocations in the films by two orders of magnitude (in respect to the substrate material), down to the value of 107cm−2, was achieved.