Determination of growth parameters for atomic layer epitaxy using reflectance difference spectroscopy

1996 ◽  
Vol 74 (S1) ◽  
pp. 85-88 ◽  
Author(s):  
R. Arès ◽  
C. A. Tran ◽  
S. P. Watkins
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Gas Flows ◽  
Difference Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reflectance Difference Spectroscopy

Reflectance difference spectroscopy (RDS) has been used to monitor the anisotropy of the surface of InAs and GaAs grown by atomic layer epitaxy (ALE). Saturation of the RDS signal is observed when the surface is fully covered with one monolayer of the impinging surface species. This property is used to optimize the growth interruptions for the ALE cycle. Good correlation of the RDS saturation is observed with growth-rate measurements obtained by X-ray diffraction (XRD). When exposure times are sufficiently long for saturation to be observed in the RDS signal, a growth rate of one monolayer per cycle (1 ML/cycle) is achieved. In principle all the different growth parameters such as exposure and purge times as well as gas flows can be determined in a few cycles performed on a single substrate. Without RDS the same results would require several growth runs and time consuming X-ray characterization.

Electrochemical Atomic-Layer Epitaxy: Electrodeposition of III-V and II-VI Compound Semiconductors

1999 ◽  
Vol 581 ◽  
Author(s):  
Travis L. Wade ◽  
Billy H. Flowers ◽  
Raman Vaidyanathan ◽  
Kenneth Mathe ◽  
Clinton B. Maddox ◽  
...  
Keyword(s):  
Compound Semiconductors ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Infrared Reflection ◽  
Epitaxial Deposition ◽  
Electrochemical Atomic Layer Epitaxy

ABSTRACTElectrochemical atomic-layer epitaxy (EC-ALE) is an approach to electrodepositing thin-films of compound semiconductors. It takes advantage of underpotential deposition (UPD), deposition of a surface limited amount (a monolayer or less) of an element at a potential less negative than bulk deposition, to form a thin-film of a compound--one atomic layer at a time. Ideally, the 2-D growth mode should promote epitaxial deposition.Many II-VI and a few III-V compounds have been formed by EC-ALE. TI-VI films such as CdSe, CdS, and CdTe have been successfully formed. In addition, deposition of III-V compounds of InAs and InSb are being explored, along with initial studies of GaAs deposition. Depositions of the I-VI systems are better understood so this report will focus on the III-V's, particularly InAs and InSb.Building compounds an atomic layer at a time lends electrochemical-ALE to nanoscale technology. Deposited thickness ranged from a few nanometers to a few hundred. The films are typically characterized by atomic-force microscopy (AFM), X-ray diffraction (XRD), electron microprobe analysis (EPMA) and ellipsometry. InAs deposits are also characterized by infrared reflection absorption.

Phosphorus Passivation of GaAs

1998 ◽  
Vol 510 ◽  
Author(s):  
S.P. Watkins ◽  
X. Xu ◽  
J. Hu ◽  
R. Ares ◽  
P. Yeo ◽  
...  
Keyword(s):  
Room Temperature ◽  
Thin Layers ◽  
Difference Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Room Temperature Photoluminescence ◽  
Reflectance Difference Spectroscopy ◽  
Similar Chemical ◽  
Pl Intensity ◽  
Undoped Gaas

AbstractWe have performed a systematic study of the effect of various phosphorus passivation techniques on the room temperature photoluminescence (PL) intensity of undoped GaAs. The effects of passivation by two methods are compared: (1) the P-exchange reaction on exposure to tertiarybutylphosphine (TBP) vapour between 500-620°C, and (2) the growth of thin layers of GaP directly on GaAs. An x-ray diffraction technique was used to estimate the thickness of the passivating layers. Reflectance difference spectroscopy indicated a similar chemical origin for the two passivation methods. Both passivation techniques resulted in strong enhancements in the room temperature PL. PL intensity was observed to increase very rapidly with adsorbed P for both cases saturating at approximately 2 monolayers equivalent GaP coverage.

Electrodeposition of CU2SE thin films by Electrochemical Atomic Layer Epitaxy (EC-ALE).

2002 ◽  
Vol 744 ◽  
Author(s):  
Raman Vaidyanathan ◽  
Mkhulu K. Mathe ◽  
Patrick Sprinkle ◽  
Steve M Cox ◽  
Uwe Happek ◽  
...  
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Atomic Layer ◽  
Atomic Ratio ◽  
Atomic Layer Epitaxy ◽  
Cyclic Voltammograms ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrochemical Atomic Layer Epitaxy ◽  
Absorption Measurements

ABSTRACTElectrochemical atomic-layer epitaxy (EC-ALE) is an approach to electrodepositing thin-films of compound semiconductors. It takes advantage of underpotential deposition (UPD), deposition of a surface limited amount (a monolayer or less) of an element at a potential less negative than bulk deposition, to form a thin-film of a compound--one atomic layer at a time. Ideally, the 2-D growth mode should promote epitaxial deposition.We report the formation of compound Cu2Se, at room temperature by electrochemical atomic layer epitaxy (EC-ALE). Cyclic voltammograms were used to determine the deposition potentials of each element. An automated deposition program was used to form 750 cycles of Cu2Se thin films. Electron probe microanalysis was done to determine the stoichiometry of the thin films. X-ray diffraction of the 200 cycle deposit indicated the presence of polycrystalline Cu2Se. The atomic ratio of Cu/Se in the thin films was found to be 2. Band gap of the thin films were determined by reflection absorption measurements. The band gap of the 200 cycle Cu2Se films was found to be 1.6 eV. X-ray diffraction of 350 and 750 cycle Cu2Se films, indicated the deposits consisted of Cu3Se2 and Cu2Se.

Selective Area Heteroepitaxy of Nano-AlGaN UV Excitation Sources for Biofluorescence Application

2006 ◽  
Vol 916 ◽  
Author(s):  
Vibhu Jindal ◽  
James Grandusky ◽  
Fatemeh Shahedipour-Sandvik ◽  
Steven LeBoeuf ◽  
Joleyn Balch ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Selective Area ◽  
Mask Material ◽  
Uv Excitation ◽  
Selection Of

AbstractWe report on the selective area heteroepitaxy and facet evolution of AlGaN nanostructures on GaN/sapphire substrate using various mask materials. We also report on the challenges associated with selection of an appropriate mask material for selective area heteroepitaxy of AlGaN with varying Al composition. The shape and the growth rate of the nanostructures are observed to be greatly affected by the mask material. The evolution of the AlGaN nanostructures and Al incorporation were studied exhaustively as a function of growth parameters; including temperature, pressure, NH3 flow, total alkyl flow and TMAl/(TMAl+TMGa) ratio. The growth rate of nanostructures was reduced drastically when higher Al percentage AlGaN nanostructures were grown. The growth rates were increased for higher Al percentage AlGaN using a surfactant which resulted in a high quality pyramidal structure. As indicated by high resolution x-ray diffraction (XRD) and cathodoluminescence (CL) spectroscopy, composition of Al in the AlGaN nanostructure is significantly different from that of a thin film grown under the same growth conditions.

Surface reconstruction of GaAs (001) during OMCVD growth

1993 ◽  
Vol 344 (1673) ◽  
pp. 443-452 ◽  
Keyword(s):  
Surface Reconstruction ◽  
Atmospheric Pressure ◽  
Molecular Beam ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Difference Spectroscopy ◽  
Reflectance Difference Spectroscopy ◽  
Surface Reconstructions

Surface reconstruction of GaAs (001) during organometallic chemical vapour deposition (OMCVD) growth has been investigated with reflectance-difference spectroscopy (RDS). RD spectra reveal that surface reconstructions similar or identical to (4 x 2), (2 x 4), and c (4 x 4) that occur on surface prepared by molecular beam epitaxy (MBE) in ultrahigh vacuum (UHV) occur even in atmospheric pressure OMCVD growth environments. Based on the RDS database we established on static surfaces in UHV , we studied the structure of surfaces under both static and dynamic conditions in non-UHV ambients. We find, in contrast to previous models, that the surfaces under various non-UHV conditions exhibit dimer formation. In addition, OMCVD growth and atomic layer epitaxy (ALE) typically occur under disordered c (4 x 4)[ d (4 x 4)]-like conditions where the surface is terminated by multilayers of As. When trimethylgallium (TMG) and arsine (AsH 3 ) are supplied simultaneously, the surface structure varies as a function of the supply rates of TMG and AsH 3 , and the substrate temperature.

Selective area heteroepitaxy of nano-AlGaN ultraviolet excitation sources for biofluorescence application

2007 ◽  
Vol 22 (4) ◽  
pp. 838-844 ◽  
Author(s):  
Vibhu Jindal ◽  
James R. Grandusky ◽  
Neeraj Tripathi ◽  
Fatemeh Shahedipour-Sandvik ◽  
Steven LeBoeuf ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ultraviolet Excitation ◽  
Selective Area ◽  
Cathodoluminescence Spectroscopy ◽  
Mask Material ◽  
Selection Of

We report on the selective area heteroepitaxy and facet evolution of AlGaN nanostructures on GaN/sapphire substrate using various mask materials. We also report on the challenges associated with selection of an appropriate mask material for selective area heteroepitaxy of AlGaN with varying Al composition. The shape and the growth rate of the nanostructures are observed to be greatly affected by the mask material. The evolution of the AlGaN nanostructures and Al incorporation were studied exhaustively as a function of growth parameters including temperature, pressure, NH3 flow, total alkyl flow, and TMAl/(TMAl+TMGa) ratio. The growth rate of nanostructures was reduced drastically when higher Al percentage AlGaN nanostructures were grown. The growth rates were increased for higher Al percentage AlGaN using a surfactant, which resulted in a high-quality pyramidal structure. As indicated by high-resolution x-ray diffraction and cathodoluminescence spectroscopy, the composition of Al in the AlGaN nanostructure is significantly different from that of a thin film grown under the same growth conditions.

InAs and InGaAs Growth by Chloride Atomic Layer Epitaxy

1989 ◽  
Vol 160 ◽  
Author(s):  
H. Shimawaki ◽  
Y. Kato ◽  
A. Usui
Keyword(s):  
Growth Factor ◽  
Growth Temperature ◽  
Growth Rates ◽  
Atomic Layer ◽  
Atomic Layer Epitaxy ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Superlattice Structures ◽  
Inp Substrates

AbstractInAs chloride ALE has been carried out in detail, resulting in successful InGaAs ALE on (111)B InP substrates. InAs growth of 0.9 ML/cycle is obtained for (111)B InAs substrates at temperatures below 375 °C, while growth rates for (100) and (111)A substrates steadily decrease with increases in growth temperature. The growth rates are independent of InCI pressure at 375 °C, suggesting a self-limiting growth factor in InAs chloride ALE. (GaAs)1(InAs)1 and (GaAs)2(InAs)2 superalloys can be prepared on (111)B InP substrates at 375 °C. Growth rates and crystal compositions for both layers agree well with the values expected for ideal superalloys. The presence of superlattice structures is indicated by X-ray diffraction measurement,

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