共查询到20条相似文献,搜索用时 15 毫秒
1.
利用全固态分子束外延(MBE)方法在Ge(100)衬底上异质外延GaAs薄膜,并通过高能电子衍射(RHEED)、高分辨X射线衍射(XRD),原子力显微镜等手段研究了不同生长参数对外延层的影响.RHEED显示在较高的生长温度或较低的生长速率下,低温GaAs成核层呈现层状生长模式.同时降低生长温度和生长速率会使GaAs薄膜的XRD摇摆曲线半高宽(FWHM)减小,并降低外延层表面的粗糙度,这主要是由于衬底和外延薄膜之间的晶格失配度减小的结果. 相似文献
2.
A. Raisanen L. J. Brillson A. Franciosi R. Nicolini L. Vanzetti L. Sorba 《Journal of Electronic Materials》1995,24(3):163-169
We performed 1—2 keVcathodoluminescence measurements and He-Ne and HeCd excited photoluminescence studies of ZnSe/GaAs( 100)
heterostructures grown by molecular beam epitaxy. Our goal was to investigate the deep level electronic structure and its
connection with the heterojunction band offsets. We observed novel deep level emission features at 0.8, 0.98, 1.14, and 1.3
eV which are characteristic of the ZnSe overlayer and independent in energy of overlayer thickness. The corresponding deep
levels lie far below those of the near-bandedge features commonly used to characterize the ZnSe crystal quality. The relative
intensity and spatial distribution of the deep level emission was found to be strongly affected by the Zn/Se atomic flux ratio
employed during ZnSe growth. The same flux ratio has been shown to influence both the quality of the ZnSe overlayer and the
band offset in ZnSe/GaAs heterojunctions. In heterostructures fabricated in Se-rich growth conditions, that minimize the valence
band offset and the concentration of Se vacancies, the dominant deep level emission is at 1.3 eV. For heterostructures fabricated
in Zn-rich growth conditions, emission by multiple levels at 0.88,0.98, and 1.14 eV dominates. The spectral energies and intensities
of deep level transitions reported here provide a characteristic indicator of ZnSe epilayer stoichiometry and near-interface
defect densities. 相似文献
3.
4.
Behavior of Sn as donor species in the MBE growth of GaAs on (111)A substrates has been investigated by varying the growth
temperature from 460 to 620°C, As4:Ga flux ratio from 4 to 25, and Sn concentration from 1016 to 1020 atoms cm-3. Secondary ion mass microscopy measurements show that Sn does not surface segregate on (111)A substrates under this growth
condition, in contrast to that on (001) substrates. Sn is uniformly incorporated throughout the bulk of the grown layer for
all samples, apart from the most highly doped ones. To increase the Sn carrier concentration on the (111)A substrates, the
measured carrier concentration shows that doping should be carried out at a low growth temperature and/or high As4:Ga flux ratio. 相似文献
5.
S. K. Chan N. Liu Y. Cai N. Wang G. K. L. Wong I. K. Sou 《Journal of Electronic Materials》2006,35(6):1246-1250
Molecular beam epitaxy (MBE) via the vapor-liquid-solid (VLS) reaction was used to grow ZnSe nanowires (NWs) on (111), (100),
and (110) oriented GaAs substrates. Through detailed transmission electron microscopy (TEM) studies, it was found that 〈111〉
orientation is the growth direction for NWs with size ≥30 nm, while NWs with size around 10 nm prefer to grow along the 〈110〉
direction, with a small portion along the 〈112〉 direction. These observations have led to the realization of vertical ZnSe
NWs with size around 10 nm grown on a GaAs (110) substrate. An ordered ZnSe NW array fabricated on a GaAs (111) substrate
with a novel prepatterning method associated with plasma etching shows a high degree of ordering and a good size uniformity
of the as-grown NWs. The diameter of the NWs in the array is around 80 nm and most of them are found to orient vertically,
but some tilt to one of the six possible directions of the 〈111〉 family. 相似文献
6.
Q. Xu J. W. P. Hsu E. A. Fitzgerald J. M. Kuo Y. H. Xie P. J. Silverman 《Journal of Electronic Materials》1996,25(6):1009-1013
The surface morphology of GaAs films grown on Ge substrates is studied by scanning force microscopy. We find a dramatic difference
arising from Ga as opposed to As prelayers in the formation of anti-phase boundaries (APBs), surface features near threading
dislocations, and surface roughness, for films as thick as 1 μm. Ga prelayer samples are smooth; thin films display some APBs
with predominantly one growth domain while the 1 μm thick film displays the morphology of a homoepitaxial GaAs film. In contrast,
As prelayer samples are rough with complicated APB structures, which can be attributed to the increase in single steps during
As2 deposition. 相似文献
7.
C. E. Stutz D. C. Look E. N. Taylor J. R. Sizelove P. W. Yu 《Journal of Electronic Materials》1995,24(1):31-34
This work discusses the transition from high resistivity as-grown GaAs layers to thermally metastable low resistivity as-grown
layers by molecular beam epitaxy. This transition occurs at about 430°C and coincides with a reflective high energy electron
diffraction reconstruction change from a 2 × 1 to 2 × 4 pattern for an As4/Ga beam equivalent pressure ratio of 20. For growth temperatures in the range 350 to 430°C, room temperature Hall-effect
measurements have shown resistivities of <107 ohm-cm and photoluminescence has shown new peaks at 0.747 eV and a band from 0.708 to 0.716 eV at 4.2K, in unannealed material. 相似文献
8.
M. W. Cho K. W. Koh K. Morikawa K. Arai H. D. Jung Z. Zhu T. Yao Y. Okada 《Journal of Electronic Materials》1997,26(5):423-428
High quality ZnSe(100) substrates have been used for homoepitaxial growth by molecular beam epitaxy. A chemical pretreatment
suitable for ZnSe substrate preparation is determined from x-ray photoemission spectroscopy studies. Thermal cleaning processes
for the ZnSe(100) surface were investigated by insitu reflection high energy electron diffraction and the surface phase diagram for ZnSe(100) was obtained for the first time.
The low temperature photoluminescence spectra recorded from homoepitaxial layers exhibit unsplit free and bound exciton transitions
with strong intensities. The full widths at half maximum of the (400) x-ray diffraction spectra for ZnSe homoepitaxial layer
were 17≈31 arcsec. 相似文献
9.
Bijan Tadayon Mark E. Twigg Mohammad Fatemi Michael Y. Frankel Adriana Giordana D. Scott Katzer 《Journal of Electronic Materials》1995,24(11):1753-1758
We present the results of a study of GaAs material grown at substrate temperatures below 250°C (low range GaAs) by molecular
beam epitaxy. This material is amorphous and highly resistive and can be converted to single crystal through annealing process.
The crystallization process is investigated by transmission electron microscopy, reflection high-energy electron diffraction,
and double-crystal x-ray diffraction techniques. 相似文献
10.
N. K. Dhar C. E. C. Wood P. R. Boyd H. K. Pollehn M. Martinka J. D. Benson J. H. Dinan 《Journal of Electronic Materials》1995,24(9):1041-1046
Amorphous layers of CdTe deposited on Cd or Zn terminated GaAs {001} surfaces can be recrystallized above ∼200°C. Subsequent
molecular beam epitaxy of CdTe proceeds in a two-dimensional mode and leads to layers which are specular and single domain
{0011}. Threading dislocation density in these layers was 1–2 x 105 cm−2. Values of full width at half maximum for x-ray rocking curves were as low as 80 arc-s. 相似文献
11.
Q. Xu J. W. P. Hsu S. M. Ting E. A. Fitzgerald R. M. Sieg S. A. Ringel 《Journal of Electronic Materials》1998,27(9):1010-1016
The surface morphology of GaAs films grown on offcut Ge substrates is studied using a scanning force microscope (SFM). We
investigated the effects of the Ge buffer layer, growth temperature, film thickness, and prelayer on the GaAs surface morphology.
The starting Ge substrates are offcut 6° toward the [110] direction to minimize single steps on the substrates before molecular
beam epitaxial film growth. We find that comparing with GaAs samples grown without Ge buffer layers or with unannealed Ge
buffer layers, samples with annealed Ge buffer layers are much smoother and contain no antiphase boundaries (APBs) on the
surface. For thick (≥1 μm) GaAs films with an annealed Ge buffer layer, the surfaces display crosshatch lines and elongated
mounds (along
, which are associated with the substrate offcut direction. As the film thickness increases, the crosshatch lines become shorter,
denser and rougher, and the mounds grow bigger (an indication of GaAs homoepitaxial growth). We conclude that annealed Ge
buffer layers are crucial for growing high quality GaAs films with few APBs generated during the growth. In addition, under
optimal conditions, different prelayers make little difference for thick GaAs films with annealed Ge buffer layers. 相似文献
12.
We study the plasma-assisted molecular beam epitaxy of cubic GaN on GaAs(OOl) substrates by means ofin-situ reflection high-energy electron diffraction. The epilayers are characterized by x-ray diffraction, photoluminescence, and
Hall measurements, and it is found that the overall best films are grown under a N/Ga ratio close to one. For anin-situ determination of the N/Ga ratio, the growth kinetics is studied via surface reconstruction transitions. The effective N flux
giving rise to growth is measured using the transient behavior of the half-order diffraction streak intensity for various
plasma operating conditions. 相似文献
13.
K. Kobayashi T. Takebe T. Yamamoto M. Fujii M. Inai D. Lovell 《Journal of Electronic Materials》1993,22(2):161-164
The properties of single quantum well (SQW) structures on (111)A GaAs grown by molecular beam epitaxy (MBE) have been investigated.
The interface abruptness of SQWs is estimated to be less than one monolayer through full width at half maximum measurements
of photoluminescence. The novel lateral p-n junctions have been formed by MBE growth of silicon-doped GaAs on (111)A substrates
patterned with equilateral triangles on the basis of these high-quality (111)A GaAs films. The idea of the lateral p-n junctions
with a triangular p-type region bounded by three equivalent n-type slopes is based on the threefold symmetry of the (111)A
surface and the acceptor nature of the silicon dopant on that surface. The lateral p-n junctions have been confirmed spatially-resolved
cathodeluminescence and current-voltage measurements. 相似文献
14.
本文从第一原理出发,用Linearized-Muffin-Tin(LMTO)能带方法对应变超晶格(ZnSe)n/(Si2)n(110)(n=2-7)进行自洽计算,在此基础上采用冻结势计算了应变异质结ZnSe/Si2(110)的价带带阶,得到其理论值为0.93eV,说明该异质结的价带带阶值较大,由其构成的量子阱对空穴运动有较强的限制作用。 相似文献
15.
We have studied the properties of molecular beam epitaxially (MBE)-grown Erdoped III-V semiconductors for optoelectronic applications.
Optically excited Er3+ in insulating materials exhibits optical emission chiefly around 1.54 μm, in the range of minimum loss in silica fiber. It
was thought, therefore, that an electrically pumped Er-doped semiconductor laser would find great applicability in fiber-optic
communication systems. Exhaustive photoluminescence (PL) characterization was conducted on several of As-based III-V semiconductors
doped with Er, on bulk as well as quantum-well structures. We did not observe any Errelated PL emission at 1.54 μm for any
of the materials/structures studied, a phenomenon which renders impractical the realization of an Er-doped III-V semiconductor
laser. Deep level transient spectroscopy studies were performed on GaAs and AlGaAs co-doped with Er and Si to investigate
the presence of any Er-related deep levels. The lack of band-edge luminescence in the GaAs:Er films led us to perform carrier-lifetime
measurements by electro-optic sampling of photoconductive transients generated in these films. We discovered lifetimes in
the picosecond regime, tunable by varying the Er concentration in the films. We also found the films to be highly resistive,
the resistivity increasing with increasing Er-concentration. Intensive structural characterization (double-crys-tal x-ray
and transmission electron microscopy) performed by us on GaAs:Er epilayers indicates the presence of high-density nanometer-sized
ErAs precipitates in MBE-grown GaAs:Er. These metallic nanoprecipitates probably form internal Schottky barriers within the
GaAs matrix, which give rise to Shockley-Read-Hall recombination centers, thus accounting for both the high resistivities
and the ultrashort carrier lifetimes. Optoelectronic devices fabricated included novel tunable (in terms of speed and responsivity)
high-speed metal-semiconductor-metal (MSM) photodiodes made with GaAs:Er. Pseudomorphic AlGaAs/ InGaAs modulation doped field
effect transistors (MODFETs) (for high-speed MSM-FET monolithically integrated optical photoreceivers) were also fabricated
using a GaAs:Er buffer layer which substantially reduced backgating effects in these devices. 相似文献
16.
Zhichuan Niu Richard Nötzel Uwe Jahn Hans-Peter Schönherr Jörg Fricke Klaus H. Ploog 《Journal of Electronic Materials》1999,28(1):1-5
The formation of triangular-shaped dot-like (TD) structures grown by molecular beam epitaxy on GaAs (311)A substrates patterned
with square- and triangular-shaped holes is compared. On substrates patterned with square-shaped holes, TD structures are
formed via the pinch-off of two symmetrically arranged {111} planes which develop freely in the regions between the holes
on the original substrate surface, while the (111)A sidewalls of the as-etched holes develop a rough morphology during growth.
The evolution of the rough (111)A sidewalls is eliminated on substrates patterned with triangular shaped holes resulting in
similar TD structures with highly improved uniformity over the entire pattern. Spectrally and spatially resolved cathodoluminescence
spectroscopy reveals the lateral variation of the quantum-well confinement energy in the TD structures generating distinct
lateral energy barriers between the top portion and the nearby smooth regions with efficient radiative recombination. Formation
of TD structures provides a new approach to fabricate three-dimensionally confined nanostructures in a controlled manner. 相似文献
17.
X. J. Wang Y. B. Hou Y. Chang C. R. Becker R. F. Klie S. Sivananthan 《Journal of Electronic Materials》2009,38(8):1776-1780
ZnTe was grown on GaAs(211)B by molecular beam epitaxy (MBE). Structural properties and strain relaxation at the ZnTe/GaAs(211)B
interface were investigated by high resolution transmission electron microscopy (HRTEM) and scanning transmission electron
microscopy (STEM). Application of digital image processing involving a filtered inverse fast Fourier transformation revealed
an array of misfit dislocations at the interface and allowed strain relaxation to be estimated. Only one twin defect was observed
in the HRTEM images, and details of this twin defect were investigated by STEM. 相似文献
18.
R. M. Sieg S. A. Ringel S. M. Ting E. A. Fitzgerald R. N. Sacks 《Journal of Electronic Materials》1998,27(7):900-907
The nucleation and growth of GaAs films on offcut (001) Ge wafers by solid source molecular beam epitaxy (MBE) is investigated,
with the objective of establishing nucleation conditions which reproducibly yield GaAs films which are free of antiphase domains
(APDs) and which have suppressed Ge outdiffusion into the GaAs layer. The nucleation process is monitored by in-situ reflection high energy electron diffraction and Auger electron spectroscopy. Several nucleation variables are studied, including
the state of the initial Ge surface (single-domain 2×1 or mixed-domain 2×1:1×2), the initial prelayer (As, Ga, or mixed),
and the initial GaAs growth temperature (350 or 500°C). Conditions are identified which simultaneously produce APD-free GaAs
layers several microns in thickness on Ge wafers with undetectable Ge outdiffusion and with surface roughness equivalent to
that of GaAs/GaAs homoepitaxy. APD-free material is obtained using either As or Ga nucleation layers, with the GaAs domain
dependent upon the initial exposure chemical species. Key growth steps for APD-free GaAs/Ge growth by solid source MBE include
an epitaxial Ge buffer deposited in the MBE chamber to bury carbon contamination from the underlying Ge wafer, an anneal of
the Ge buffer at 640°C to generate a predominantly double atomic-height stepped surface, and nucleation of GaAs growth by
a ten monolayer migration enhanced epitaxy step initiated with either pure As or Ga. We identify this last step as being responsible
for blocking Ge outdiffusion to below 1015 cm−3 within 0.5 microns of the GaAs/Ge interface. 相似文献
19.
The crystallographic orientation of low temperature (LT) grown CaF2 on GaAs (100) substrates is investigated. LT epitaxial (100) CaF2 layers are obtained on a thin (100) oriented CaF2 template at growth temperatures down to room temperature. This makes it possible to grow crack-free CaF2 (100) using a multiple-temperature-growth scheme at any desired temperature. The resulting CaF2 layers, with thickness up to 680 nm, can withstand temperature cycling from RT to 650°C without cracking. Based on these
results, a four pair Ga0.5Al0.5As/CaF2 quarter-wavelength Bragg reflector was fabricated with center wavelength at 880 nm. The reflector, with a total CaF2 thickness of 615 nm, shows broadband high reflectivity with a crack-free surface. This crack-free surface can then be overgrown
with further device layers. 相似文献
20.
S. P. Ahrenkiel M. H. Bode M. M. Al-Jassim H. Luo S. H. Xin J.K Furdyna 《Journal of Electronic Materials》1995,24(4):319-325
Molecular beam epitaxial growth of the ZnSe1-xTex (x=0.44-0.47) alloy on vicinal (001) GaAs substrates tilted four, six, and nine degree-[111]A or B results in partial phase separation of the alloy with a vertical modulation between different compositions. Transmission electron microscopy images of samples grown on four degree-tilted substrates showed superlattice-like structures, with periods in the range 13.4-28.9Â. Lattice images reveal diffuse interfaces between light and dark bands. Period variations were detected in isolated regions of some samples. We present evidence that the modulation develops at the growth surface, and remains stable in the bulk at temperatures up to 450°C. Satellite spot pairs with approximate indices (h k 1 + δ) were present near the zinc-blende spots in electron diffraction patterns and x-ray diffraction data, as expected from material with a sinusoidal composition profile. The orientation of the spots reveals that the modulation vector is parallel to the growth direction, rather than to [001]. The [111]A- and B-tilted samples showed significant modulation, while the five degree-[110] and on-axis material showed no detectable modulation. The modulation wavelength did not strongly depend on growth temperature in the range examined (285–335°C). Samples showing composition modulation did not exhibit significantly altered low-temperature luminescence spectra from material with no modulation. 相似文献