Characterization Of Epilayers Research Articles

Impacts of oxygen source on band alignment of ALD Al2O3/(α-, ε-)Ga2O3 interface

Al2O3 films were deposited on α- and ε-Ga2O3 films by atomic layer deposition (ALD) in different plasma oxygen source (H2O, O3, O2 plasma). The α- and ε-Ga2O3 films were epitaxially grown on sapphire substrates by mist chemical vapor deposition (Mist-CVD) and pulsed laser deposition (PLD), respectively. The epilayer characteristics were investigated by high resolution X-ray diffraction (HRXRD), atomic force microscope (AFM) and high resolution transmission electron microscopy (HRTEM). Furthermore, the energy band diagrams of Al2O3/α-Ga2O3 and Al2O3/ε-Ga2O3 were investigated by X-ray photoelectron spectroscopy (XPS). On the basis of Ga 3d and Al 2p core-level spectra as well as α- and ε-Ga2O3 valence band spectra, the energy band diagrams of Al2O3/α-Ga2O3 and Al2O3/ε-Ga2O3 interface were determined. And the conduction band offset of Al2O3/α-Ga2O3 interfaces were estimated to be 1.21/1.31/1.27 eV for oxidant of H2O, O3 and O2 plasma, respectively, while that of Al2O3/ε-Ga2O3 were 1.61/1.72/1.7 eV, the conduction band offsets of Al2O3 grown by O3 and O2 plasma were higher than those grown by H2O. And, the conduction band offsets of all samples were greater than 1 eV, indicating that Al2O3 grown by ALD can be used as gate dielectric in (α-, ε-) Ga2O3 power device.

Characterization of Epilayers in Vertical Light-Emitting Diode Grown by Mixed-Source Hydride Vapor Phase Epitaxy

Characterization of Epilayers in Vertical Light-Emitting Diode Grown by Mixed-Source Hydride Vapor Phase Epitaxy

Verification of threading dislocations density estimation methods suitable for efficient structural characterization of AlxGa1−xN/GaN heterostructures grown by MOVPE

Selection of a suitable chemical etching method for threading dislocations density estimation is crucial for the structural characterization of epilayers grown by MOVPE and thus further for device fabrication. In this work, threading dislocations density in single layer and AlxGa1−xN/GaN periodical heterostructures has been investigated by means of chemical etching and XRD analysis. For chemical etching, two types of agents have been used: phosphoric acid (220°C/7.5min) and a molten mixture of KOH-NaOH (440°C/2.5min). Estimation of dislocation density has been carried out on the basis of SEM images. It was shown that defect-selective etching in molten alkaline solution is more effective than etching in phosphoric acid and provides more accurate data that are in agreement with data obtained from XRD characterization.

Growth and characterization of epilayer of SiC on Si (111) substrate using single solid source MBE

3C-SiC thin films have been grown by Molecular Beam Epitaxial (MBE) technique on a Si (111) substrate at 1050°C using a single solid source fullerene (C60). Fullerene molecules adsorb on the tissue like surface of substrate and then thermally decompose into amorphous carbon and produce 3C-SiC. The grown films were characterized by SEM/EDX, XRD, FTIR and Raman spectroscopy. XRD data confirmed the growth of thick, highly crystalline and epitaxial SiC. The grown film has amorphous surface but the inner core consists of nearly perfect crystalline lattice structure indicated by SEM. FTIR and Micro-Raman also confirmed the high crystalline growth of 3C-SiC . The method proves to be a milestone for low temperature and high crystalline growth of 3C-SiC.

Chloride vapor-phase epitaxy of gallium nitride on silicon: Structural and luminescent characteristics of epilayers

The structure and luminescent properties of gallium nitride (GaN) epilayers grown by hydride-chloride vapor-phase epitaxy (HVPE) in a hydrogen or argon atmosphere on 2-inch Si(111) substrates with AlN buffer layers have been studied. The replacement of hydrogen atmosphere by argon for the HVPE growth of GaN leads to a decrease in the epilayer surface roughness. The ratio of intensities of the donor-acceptor and exciton bands in the luminescence spectrum decreases with decreasing growth temperature. For the best samples of GaN epilayers, the halfwidth (FWHM) of the X-ray rocking curve for the (0002) reflection was 420 sec of arc, and the FWHM of the band of exciton emission at 77 K was 48 meV.

Advances in 4H-SiC Homoepitaxy for Production and Development of Power Devices

AbstractIn this paper we present results of epitaxial layer deposition for production needs using our hot-wall CVD multi-wafer system. This equipment exhibits a capacity of 7x3” wafers per run and can be upgraded to a 6x4” setup. Characteristics of epilayers and reproducibility of the proc-esses are reported. Furthermore, we show recent results of p-type SiC homoepitaxial growth on 3” 4° off-oriented substrates using a single-wafer hot-wall CVD. The dependence of layer prop-erties on growth parameters, doping and thickness uniformity as well as doping memory effects are discussed. For the characterization of epitaxially grown pn-junctions first research grade pin-diodes were fabricated. The p-type emitters were either deposited in the same growth run to-gether with the n-type buffer and drift layers (continuous growth) or the n- and p-layers were grown in two different growth runs (separate growth).

Electron cyclotron resonance plasma preparation of CdZnTe (211)B surfaces for HgCdTe molecular beam epitaxy

CdZnTe wafers were inserted into a multi-chamber processing facility without prior preparation, cleaned by exposure to an electron cyclotron resonance Ar/H2 plasma, and used as substrates for molecular beam epitaxy of HgCdTe. Changes induced in the wafer near-surface region during the cleaning step were monitored using in situ spectroscopic ellipsometry. Ellipsometric data were subsequently modeled to provide the time evolution of the thickness of a native overlayer. Auger electron spectra were consistent with surfaces free of residual contamination and which had the stoichiometry of the underlying bulk. Surface roughness values of 0.4 nm were obtained ex situ using interferometric microscopy. Electron diffraction patterns of plasma prepared wafers heated to 185°C (the temperature required for HgCdTe molecular beam epitaxy) were streaked. Structural and electrical characteristics of epilayers grown on these substrates were found to be comparable to those deposited on wafers prepared using a conventional wet chemical process. This demonstrates an important step in an all-vacuum approach to HgCdTe detector fabrication.

Atomic layer epitaxy of AlAs and (AlAs) n(GaAs) n superlattices with a new aluminum source ethyldimethylamine alane

We describe the successful ALE growths of AlAs and (AlAs) n (GaAs) n superlattices (SLs) with reduced carbon content by using ethyldimethylamine alane as a new aluminum source. X-ray diffraction and Raman scattering measurements reveal that the AlAs GaAs interface is reasonably smooth for the SLs with n ≥ 3 while it becomes rough for those with n ≤ 2. Through the growth and characterization of epilayers and SLs, we discuss the advantage of this new aluminum source as well as unsolved problems in the ALE of the AlAsGaAs system.

Low Pressure MOVPE Photo-Assisted Growth of ZnxCd1-xS

ABSTRACTWe will report the photo-assisted heteroepitaxial growth of Znx Cdl-xS by Metalorganic Vapor Phase Epitaxy (MOVPE). Sources materials were diethylzinc, dimethylcadmium and tertiaributylmercarptan. We have studied the effect of light intensity on the change of the Zn composition, crystalline quality and optical properties of epitaxial layers grown on (100) GaAs substrates. The Zn composition of the films could be increased by ≃ 15% by illuminating layers during the growth at 400°C. Concerning the characterization of epilayers, we observed a bright luminescence peak at E = 2.80 eV for x≃ 0.4. Epilayers with the best crystalline quality we could grown exhibited a full width at half maximum of ≃ 70 arsec by x-ray diffraction rocking curves when grown at 380°C.

HgCdTe Crystal Growth by ]Molecular Beam Epitaxy and Characteristics of Epilayers

HgCdTe Crystal Growth by ]Molecular Beam Epitaxy and Characteristics of Epilayers

High resolution transmission and analytical electron microscopy for the characterisation of epilayers and interfaces in MOVPE grown ZnSe 1− yS y

Epitaxial layers of the system ZnSe 1− y S y (O ⩽ y ⩽ 1) have been grown by MOVPE (metal-organic vapour phase epitaxy). High resolution transmission (lattice imaging) and analytical electron microscopy have been employed for the structural and compositional investigation of bulk epitaxial layers and the interfaces. In the bulk, micro-twins have been characterised and the development of these from stacking faults is discussed. Interfaces between ZnSe and ZnSe 0.90S 0.10 have been investigated and their quality is found to be very dependent on the method of gas switching employed. The structural quality of the materials improves with the number of layers grown.