TEM Investigations of CdTe/GaAs(001) Interfaces

1992 ◽  
Vol 281 ◽  
Author(s):  
J. E. Angelo ◽  
W. W. Gerberich ◽  
G. Bratina ◽  
L. Sorba ◽  
A. Franciosi
Keyword(s):  
Molecular Beam Epitaxy ◽  
Defect Structure ◽  
Molecular Beam ◽  
Interfacial Structure ◽  
Buffer Layers ◽  
Gaas Surface ◽  
Ex Situ ◽  
Etch Pits ◽  
Oriented Growth ◽  
Cross Sectional

ABSTRACTIn this study, cross-sectional transmission electron microscopy (XTEM) was used to investigate the defect structure which occurs at the interface between CdTe(001) and GaAs(001). The heterostructures were fabricated by molecular beam epitaxy on chemically etched and thermally deoxidized GaAs(001) substrates as well as GaAs(001) buffer layers grown in-situ by molecular beam epitaxy. This allowed for investigation of the GaAs surface preparation on the subsequent interfacial structure. The as-etched substrate led to a microscopically rough interface with the CdTe depositing in etch pits on the GaAs surface, while growth on the buffer layer led to a macroscopically flat interface. Further, growth was accomplished on different Te-induced surface reconstructions ((6×1) vs (2×1)) in an effort to understand the role of the precursor surface treatment on the subsequent interfacial structure. In this case growth on the (6×1) reconstruction led to the introduction of (111)-oriented inclusions at the interface, while the (2×1) reconstruction led to pure (001)-oriented growth. A mechanism for the formation of planar defects at the CdTe/GaAs(001) interface is described which is based on local misorientations of the CdTe and GaAs. Finally, preliminary results of ex-situ annealing experiments on the interfacial defect structure will be discussed.

Tem Investigations of CdTe/GaAs(001) Interfaces

1993 ◽  
Vol 319 ◽  
Author(s):  
J.E. Angelo ◽  
W.W. Gerberich ◽  
G. Bratina ◽  
L. Sorba ◽  
A. Franciosi ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Defect Structure ◽  
Molecular Beam ◽  
Misfit Strain ◽  
Growth Direction ◽  
Film Structure ◽  
Buffer Layers ◽  
Ex Situ ◽  
Cross Sectional ◽  
Transmission Electron

AbstractIn this study, cross-sectional transmission electron microscopy (XTEM) was used to investigate the defect structure at the interface between CdTe(001) and GaAs(001) as well as CdTe(1 11) and GaAs(001). The heterostructures were fabricated by molecular beam epitaxy on GaAs(001) buffer layers grown in-situ by molecular beam epitaxy. The defect structure at the as-deposited CdTe(001)/GaAs(001) interface consists of both dislocations and planar faults. The planar faults are both microtwins and stacking faults. It is found that annealing of the film ex-situ causes a restructuring of the CdTe near the interface, with the microtwins being completely removed upon annealing to 450°C for 100 hours. The CdTe(111)/GaAs(001) thin film structure consists of a large number of microtwins parallel to the growth direction. This twinned structure is shown to be related to the relaxation of a residual misfit strain normal to the twin direction. Possible mechanisms for the relaxation are discussed.

Ge Nanocrystals Grown on Si(111) by Molecular Beam Epitaxy with and without CaF2 Buffer Layers

1994 ◽  
Vol 358 ◽  
Author(s):  
Peter W. Deelman ◽  
Thomas Thundat ◽  
Leo J. Schowalter
Keyword(s):  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Ex Situ ◽  
Rheed Pattern ◽  
Island Growth ◽  
Clustering Behavior ◽  
Ge Nanocrystals

ABSTRACTThe Stranski-Krastanov growth mode of Ge thin films on Si and the clustering behavior of Ge on calcium fluoride have been exploited to grow self-assembled nanocrystals by molecular beam epitaxy. The growth of the samples was monitored in situ with RHEED, and they were analyzed ex situ with AFM and RBS. For each system (Ge/Si and Ge/CaF2/Si), the dependence of Ge islanding on substrate temperature and on substrate misorientation was studied. When grown on Si(111) at temperatures between 500°C and 700°C, Ge clusters nucleated at step edges on vicinal wafers and nucleated homogeneously on on-axis wafers. Above 600°C, no transition to a spotty RHEED pattern, which would be expected for island growth, was observed for the vicinal samples. Ge grown at 500°C on on-axis Si(111) formed islands with a relatively narrow size distribution, typically 160nm in diameter and 10nm to 20nm in height. When grown on a CaF2 buffer layer, Ge islands nucleated homogeneously at a substrate temperature of 750°C, resulting in randomly distributed, oblate crystallites approximately 100nm to 200nm in diameter. At 650°C and 700°C, although we still observed many randomly distributed, small crystallites, most islands nucleated at step bunches and had a length scale of over 500nm.

Gas Source Molecular Beam Epitaxy of ZnSe on (In,Ga)P

1994 ◽  
Vol 340 ◽  
Author(s):  
K. Lu ◽  
P.A. Fisher ◽  
E. Ho ◽  
J.L. House ◽  
G.S. Petrich ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Critical Thickness ◽  
Buffer Layers ◽  
Ex Situ ◽  
Material System ◽  
Lattice Constants ◽  
Gas Source ◽  
Gaas Substrates ◽  
Lattice Matched

ABSTRACTThe wide bandgap semiconductor ZnSe has been nucleated on epitaxial (In,Ga)P buffer layers (on GaAs substrates) having various In compositions, and hence various lattice constants. The III-V ternary alloy offers a wide range of lattice constants for the heteroepitaxy of a multitude of potential II-VI light emitting devices, such as blue pn injection lasers composed of the (Zn,Mg)(S,Se) material system. Since the II-VI and III-V layers are grown using gas source molecular beam epitaxy in separate dedicated reactors, the technique of amorphous As deposition is employed to passivate the (In,Ga)P surface prior to the ex situ transfer. High resolution double crystal x-ray diffraction measurements on the ZnSe/(In,Ga)P/GaAs heterostructures indicate that for In compositions of 50-52%, the buffer layers with a thickness of 4 μm were only partially relaxed on the GaAs substrates, with the residual mismatch remaining at the ZnSe/III-V heterointerface. The critical thickness of (In,Ga)P, with In concentrations near 52-56%, on GaAs greatly exceeds the predicted critical thickness from either the energy balancing or force balancing model. For an In composition of 56% (and a film thickness of 4 μm), the buffer layers contain an in-plane lattice constant equal to that of ZnSe, and therefore represent the lattice-matched condition, even though the film is not fully relaxed. For (In,Ga)P buffer layers lattice-matched to ZnSe, but mismatched to GaAs, the surface exhibits the expected cross-hatched surface morphology. The occurrence of the cross-hatched surface is significantly alleviated by the addition of a pseudomorphic layer of GaAs positioned between the ZnSe and (In,Ga)P layer.

Real-Time Monitoring by Spectroscopic Ellipsometry and Desorption Mass Spectroscopy During Molecular Beam Epitaxy of AlGaAs/GaAs at High Substrate Temperatures

1999 ◽  
Vol 569 ◽  
Author(s):  
W. T. Taferner ◽  
K. Mahalingam ◽  
D. L. Dorsey ◽  
K. G. Eyink
Keyword(s):  
Molecular Beam Epitaxy ◽  
Mass Spectroscopy ◽  
Spectroscopic Ellipsometry ◽  
Molecular Beam ◽  
Elevated Temperatures ◽  
Gaas Layer ◽  
Ex Situ ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Substrate Temperatures

ABSTRACTA series of AlGaAs/GaAs depositions were monitored in-situ by spectroscopic ellipsometry and desorption mass spectroscopy, under various substrate temperatures (890 K - 990 K) where non-unity sticking conditions occur. An upper bound on the temperature where AlGaAs/GaAs heterostructures may be grown was determined. Ex-situ cross-sectional transmission electron microscopy verified that the AlGaAs/GaAs layer thicknesses grown by molecular beam epitaxy were accurately determined by spectroscopic ellipsometry at these elevated temperatures. The substrate temperature dependence on Ga desorption rates was consistent with Monte Carlo simulation where desorption from both physisorbed and chemisorbed states were included.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

scholarly journals Investigation of GaAs surface treatments for ZnSe growth by molecular beam epitaxy without a buffer layer

2021 ◽  
Vol 549 ◽  
pp. 149245
Author(s):  
Chaomin Zhang ◽  
Kirstin Alberi ◽  
Christiana Honsberg ◽  
Kwangwook Park
Keyword(s):  
Molecular Beam Epitaxy ◽  
Buffer Layer ◽  
Molecular Beam ◽  
Surface Treatments ◽  
Gaas Surface

Ex Situ Thermal Cycle Annealing of Molecular Beam Epitaxy Grown HgCdTe/Si Layers

2009 ◽  
Vol 39 (1) ◽  
pp. 43-48 ◽  
Author(s):  
S. Farrell ◽  
G. Brill ◽  
Y. Chen ◽  
P. S. Wijewarnasuriya ◽  
Mulpuri V. Rao ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Thermal Cycle ◽  
Molecular Beam ◽  
Ex Situ ◽  
Thermal Cycle Annealing

Properties of Epitaxial SrTiO3 Thin Films Grown on Silicon by Molecular Beam Epitaxy

1999 ◽  
Vol 567 ◽  
Author(s):  
Z. Yu ◽  
R. Droopad ◽  
J. Ramdani ◽  
J.A. Curless ◽  
C.D. Overgaard ◽  
...  
Keyword(s):  
Thin Films ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
High Energy ◽  
State Density ◽  
Unit Cell ◽  
Ex Situ ◽  
Silicon Oxide Layer ◽  
Single Crystalline ◽  
X Ray

ABSTRACTSingle crystalline perovskite oxides such as SrTiO3 (STO) are highly desirable for future generation ULSI applications. Over the past three decades, development of crystalline oxides on silicon has been a great technological challenge as an amorphous silicon oxide layer forms readily on the Si surface when exposed to oxygen preventing the intended oxide heteroepitaxy on Si substrate. Recently, we have successfully grown epitaxial STO thin films on Si(001) surface by using molecular beam epitaxy (MBE) method. Properties of the STO films on Si have been characterized using a variety of techniques including in-situ reflection high energy electron diffraction (RHEED), ex-situ X-ray diffraction (XRD), spectroscopic ellipsometry (SE), Auger electron spectroscopy (AES) and atomic force microscopy (AFM). The STO films grown on Si(001) substrate show bright and streaky RHEED patterns indicating coherent two-dimensional epitaxial oxide film growth with its unit cell rotated 450 with respect to the underlying Si unit cell. RHEED and XRD data confirm the single crystalline nature and (001) orientation of the STO films. An X-ray pole figure indicates the in-plane orientation relationship as STO[100]//Si[110] and STO(001)// Si(001). The STO surface is atomically smooth with AFM rms roughness of 1.2 AÅ. The leakage current density is measured to be in the low 10−9 A/cm2 range at 1 V, after a brief post-growth anneal in O2. An interface state density Dit = 4.6 × 1011 eV−1 cm−2 is inferred from the high-frequency and quasi-static C-V characteristics. The effective oxide thickness for a 200 Å STO film is around 30 Å and is not sensitive to post-growth anneal in O2 at 500-700°C. These STO films are also robust against forming gas anneal. Finally, STO MOSFET structures have been fabricated and tested. An extrinsic carrier mobility value of 66 cm2 V−11 s−1 is obtained for an STO PMOS device with a 2 μm effective gate length.

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