Comparison of the crystalline quality of step-graded and continuously graded InGaAs buffer layers

ABSTRACTThe influence of growth temperature on oxygen incorporation into GaN epitaxial layers was studied. GaN layers deposited at low temperatures were characterized by much higher oxygen concentration than those deposited at high temperature typically used for epitaxial growth. GaN buffer layers (HT GaN) about 1 μm thick were deposited on GaN nucleation layers (NL) with various thicknesses. The influence of NL thickness on crystalline quality and oxygen concentration of HT GaN layers were studied using RBS and SIMS. With increasing thickness of NL the crystalline quality of GaN buffer layers deteriorates and the oxygen concentration increases. It was observed that oxygen atoms incorporated at low temperature in NL diffuse into GaN buffer layer during high temperature growth as a consequence GaN NL is the source for unintentional oxygen doping.

Download Full-text

Magnetic characterization of (001) and (111) Ni films epitaxially grown on MgO

MRS Proceedings ◽

10.1557/proc-674-t1.7 ◽

2001 ◽

Vol 674 ◽

Author(s):

R. A. Lukaszew ◽

V. Stoica ◽

R. Clarke

Keyword(s):

Film Growth ◽

Chemical Interaction ◽

Hysteresis Loops ◽

Magnetic Thin Films ◽

Magnetic Films ◽

Buffer Layers ◽

Crystalline Quality ◽

Silicon Substrates

ABSTRACTOne interesting application of epitaxial magnetic thin films is to use them as one of the electrodes in a spin-dependent tunneling junction, in order to use the magnetocrystalline anisotropy to define the required two states of the magnetization. [1] In our preliminary work, we prepared epitaxial magnetic films on copper buffer layers grown on silicon substrates. [2] The single crystalline quality of the films was particularly evident in the magnetization hysteresis loops, showing a sharp reversal at fairly high fields (120 Oe), when the samples were magnetized along the crystallographic easy axis. One technological disadvantage in this type of samples is the chemical interaction between the metallic layers and the silicon substrate.In order to explore the possibility of epitaxial magnetic films on less reactive substrates, we studied the growth on MgO substrates. We have shown that it is possible to obtain epitaxial (001) and (111) Ni films grown on MgO substrates. [3] In particular we observed that the crystalline quality of the films improved considerably after 10 nm of film growth. We will now present our studies on the magnetic properties of these films, particularly the azimuthal dependence of the magnetization reversal using MOKRE, correlating our finding with the structural characterization obtained with RHEED, STM and XRD.

Download Full-text

Effects of the Nitridation Process of (0001) Sapphire on Crystalline Quality of InN Grown by RF-MBE

MRS Proceedings ◽

10.1557/proc-831-e4.2 ◽

2004 ◽

Vol 831 ◽

Cited By ~ 4

Author(s):

Daisuke Muto ◽

Ryotaro Yoneda ◽

Hiroyuki Naoi ◽

Masahito Kurouchi ◽

Tsutomu Araki ◽

...

Keyword(s):

Low Temperature ◽

Buffer Layer ◽

Buffer Layers ◽

Crystalline Quality ◽

Constant Independent ◽

Nitrogen Flux ◽

Sapphire Substrates ◽

Nitridation Process ◽

Flux Modulation

ABSTRACTThe effects of the nitridation process of (0001) sapphire on crystalline quality of InN were clearly demonstrated. The InN films were grown on NFM (nitrogen flux modulation) HT-InN or LT-InN buffer layers, which had been deposited on nitridated sapphire substrates. We found that low-temperature nitridation of sapphire is effective in improving the tilt distribution of InN films. Whereas the twist distribution remained narrow and almost constant, independent of nitridation conditions, when LT-InN buffer layers were used. The XRC-FWHM value of 54 arcsec for (0002) InN, the lowest reported to date, was achieved by using the LT-InN buffer layer and sapphire nitridation at 300°C for 3 hours.

Download Full-text

Improved crystalline quality of ZnO with inserting multi-buffer layers

Journal of Materials Science Materials in Electronics ◽

10.1007/s10854-020-03542-0 ◽

2020 ◽

Vol 31 (13) ◽

pp. 9982-9988 ◽

Cited By ~ 2

Author(s):

Sujun Guan ◽

Akihiro Mori ◽

Mikihiro Kato ◽

Xinwei Zhao

Keyword(s):

Buffer Layers ◽

Crystalline Quality

Download Full-text

Improvements in crystalline quality of thick GaN layers on GaAs (111)A by periodic insertion of low-temperature GaN buffer layers

physica status solidi (c) ◽

10.1002/pssc.200303503 ◽

2003 ◽

Vol 0 (7) ◽

pp. 2141-2144

Author(s):

H. Murakami ◽

N. Kawaguchi ◽

Y. Kangawa ◽

Y. Kumagai ◽

A. Koukitu

Keyword(s):

Low Temperature ◽

Buffer Layers ◽

Crystalline Quality

Download Full-text

Structure and Orientation of As Precipitates in LT-MBE Grown GaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088816 ◽

1991 ◽

Vol 49 ◽

pp. 900-901 ◽

Cited By ~ 1

Author(s):

Alain Claverie ◽

Zuzanna Liliental-Weber

Keyword(s):

Transport Properties ◽

Layer Thickness ◽

Growth Temperature ◽

Low Temperatures ◽

Lattice Parameter ◽

Crystalline Quality ◽

Insulating Properties ◽

Lt Gaas

GaAs layers grown by MBE at low temperatures (in the 200°C range, LT-GaAs) have been reported to have very interesting electronic and transport properties. Previous studies have shown that, before annealing, the crystalline quality of the layers is related to the growth temperature. Lowering the temperature or increasing the layer thickness generally results in some columnar polycrystalline growth. For the best “temperature-thickness” combinations, the layers may be very As rich (up to 1.25%) resulting in an up to 0.15% increase of the lattice parameter, consistent with the excess As. Only after annealing are the technologically important semi-insulating properties of these layers observed. When annealed in As atmosphere at about 600°C a decrease of the lattice parameter to the substrate value is observed. TEM studies show formation of precipitates which are supposed to be As related since the average As concentration remains almost unchanged upon annealing.

Download Full-text

GaAs avalanche photodiodes and the effect of rapid thermal annealing on crystalline quality of GaAs grown on Si by molecular-beam epitaxy

Journal of Vacuum Science & Technology B Microelectronics Processing and Phenomena ◽

10.1116/1.583761 ◽

1987 ◽

Vol 5 (3) ◽

pp. 822 ◽

Cited By ~ 32

Author(s):

N. Chand

Keyword(s):

Molecular Beam Epitaxy ◽

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Molecular Beam ◽

Avalanche Photodiodes ◽

Crystalline Quality

Download Full-text

Investigation of the Heteroepitaxial Process Optimization of Ge Layers on Si (001) by RPCVD

Nanomaterials ◽

10.3390/nano11040928 ◽

2021 ◽

Vol 11 (4) ◽

pp. 928

Author(s):

Yong Du ◽

Zhenzhen Kong ◽

Muhammet Toprak ◽

Guilei Wang ◽

Yuanhao Miao ◽

...

Keyword(s):

High Temperature ◽

Buffer Layer ◽

Layer Thickness ◽

Growth Temperature ◽

Crystalline Quality ◽

Initial Growth ◽

Two Dimensional ◽

High Quality ◽

Reduced Pressure

This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650 °C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation.

Download Full-text