共查询到20条相似文献,搜索用时 31 毫秒
1.
Fereydoon Namavar N. M. Kalkhoran A. Claverie Z. Liliental-Weber E. R. Weber P. A. Sekula-Moisé S. Vernon V. Haven 《Journal of Electronic Materials》1993,22(12):1409-1412
We have demonstrated the formation of arsenic precipitates in GaAs using arsenic implantation and annealing. Electrical measurements
show that very high resistivity (surface or buried) GaAs layers can be produced by this method. The arsenic-implanted materials
are similar to GaAs:As buffer layers grown by low-temperature molecular beam epitaxy, which are used for eliminating backgating
problems in GaAs circuits. Arsenic implantation is a nonepitaxial process which is compatible with current GaAs technology.
Formation of insulating GaAs layers by this technique may improve the performance and packing density of GaAs integrated circuits,
leading to advanced novel III–V compound-based technologies for high-speed and radiation-hard circuits. 相似文献
2.
Zuzanna Liliental-Weber H. J. Cheng S. Gupta J. Whitaker K. Nichols F. W. Smith 《Journal of Electronic Materials》1993,22(12):1465-1469
The relationship between the structural quality of low-temperature GaAs layers and the photoexcited carrier lifetime has been
studied. Transmission electron microscopy, x-ray rocking curves, time-resolved reflectance methods, and photoconductive-switch-response
measurements were used for this study. For a variety of samples grown at temperatures in the vicinity of 200°C, subpicosecond
carrier lifetimes were observed both in as-grown layers, as well as in the same layers after post-annealing and formation
of As precipitates. These results suggest that the carrier lifetime, which was found to be shorter in the as-grown layers
than in the annealed ones, might be related to the density of AsGa antisite defects present in the layers. The annealed layers which contained structural defects before annealing appeared
to exhibit the longest carrier lifetime due to gettering of As on these defects (and formation of relatively large As precipitates)
and depletion of extra As (AsGa) defects from the layer. It was found as well that the responsivity of detectors fabricated on these layers depended strongly
on the structural quality of the layers, with the greatest response obtained not for the layers with the fewest defects, but
for the layers with 107–108/cm2 of pyramidal defects. 相似文献
3.
A. A. Pastor U. V. Prokhorova P. Yu. Serdobintsev V. V. Chaldyshev M. A. Yagovkina 《Semiconductors》2013,47(8):1137-1140
GaAs samples grown by molecular-beam epitaxy at low (230°C) temperatures are investigated. One of the samples is subjected to aftergrowth annealing at 600°C. Using an unconventional pump-probe scheme for measuring the dynamic variation in the light refractive index, the nonequilibrium charge-carrier lifetime (275 ± 30 fs before annealing) is determined. Such a short carrier lifetime in the unannealed material is due to the high concentration of point defects, mainly AsGa antisite defects. According to X-ray diffraction and steady-state optical absorption data, the AsGa concentration in the samples is 3 × 1019 cm?3, which corresponds to an arsenic excess of 0.26 at %. Upon annealing at 600°C, the superstoichiometric As defects self-organize and form As nanoinclusions in the GaAs crystal matrix. It is shown that in this case the nonequilibrium charge-carrier lifetime increases to 452 ± 5 fs. This lifetime is apparently ensured by the capture of non-equilibrium charge carriers at metal As nanoinclusions. 相似文献
4.
J. P. Ibbetson J. S. Speck N. X. Nguyen A. C. Gossard U. K. Mishra 《Journal of Electronic Materials》1993,22(12):1421-1424
We have examined the role of As precipitates on transport through undoped GaAs grown at low temperature by molecular beam
epitaxy and annealed at high temperature. Temperature dependent I–V measurements exhibit two regimes. At temperatures less
than ∼200K, transport attributed to point defect-associated hopping conduction is observed even for samples annealed at 750°C.
For temperatures greater than ∼200K, the transport is quantitatively consistent with calculations of thermally assisted tunneling
emission of electrons from metallic As precipitates acting as buried Schottky barriers. 相似文献
5.
S. Gupta J. F. Whitaker S. L. Williamson G. A. Mourou L. Lester K. C. Hwang P. Ho J. Mazurowski J. M. Ballingall 《Journal of Electronic Materials》1993,22(12):1449-1455
GaAs grown by molecular beam epitaxy (MBE) at low substrate temperatures (≈200°C) exhibits the desired properties of a high-speed
photoconductor: high resistivity, high mobility, high dielectric-breakdown strength, and subpicosecond carrier lifetime. The
unique material properties are related to the excess arsenic content in the MBE grown epilayers. Due to the combination of
the above properties, dramatically improved performance has been observed in photoconductive detectors and correlators using
submicron spaced electrodes. In addition to GaAs, low-temperature growth of InxGa1−xAs alloys also leads to the incorporation of excess arsenic in the layers, and therefore this material system exhibits many
beneficial photoconductor properties as well. In particular, the lattice-mismatched growth of LT-InxGa1−xAs on GaAs appears to be the most suited for high-speed detector applications in the near-infrared wavelength range used in
optical communications. The material issues and the photodetector characteristics required to optimize their performance are
discussed. 相似文献
6.
研究了垂直梯度凝固法(VGF法)生长的掺Si低阻GaAs单晶材料的晶格缺陷和性质,并将VGF法和LEC法生长的非掺半绝缘GaAs单晶进行了比较. 利用A-B腐蚀显微方法比较了两种材料中的微沉积缺陷,对其形成原因进行了分析. 利用荧光光谱研究了掺Si-GaAs单晶中Si原子和B原子的占位情况和复合体缺陷. Hall测量结果表明,掺Si低阻VGF-GaAs单晶中存在很强的Si自补偿效应,造成掺杂效率降低. VGF-GaAs单晶生长过程中高的Si掺杂浓度造成晶体中产生大量杂质沉积,而杂质B的存在加重了这种现象. 对降低缺陷密度,提高掺杂效率的途径进行了分析. 相似文献
7.
G. B. Stringfellow 《Journal of Electronic Materials》1988,17(4):327-335
A major limitation to the continuing development of organometallic vapor phase epitaxy (OMVPE) for the growth of III/V semiconductor
materials is the hazard posed by the hydride sources, AsH3 and PH3, which are virtually universally used, in high pressure cylinders, as the group V source materials for the growth of the
highest quality materials. The ideal group V source would be a nontoxic liquid with a moderate vapor pressure (50-500 Torr).
To be suitable for OMVPE growth, the molecule must pyrolyze at ordinary growth temperatures, be stable against decomposition
in the bottle at room temperature, and not participate in undesirable parasitic reactions with the group III source molecules.
The new sources have additional constraints related to purity. They must be easily purified without decomposing and produce
no detectable carbon contamination in the resultant epitaxial layers. This set of stringent requirements eliminates most commonly
available non-hydride group V sources. Recent research on newly developed sources has shown considerable promise. The entire
area of group V sources, including the elemental sources, for OMVPE growth of III/V materials will be reviewed. The sources
with no hydrogen atoms attached to the group V atom, the elemental, trimethyl-V, and triethyl-V, sources all appear to give
unacceptably high carbon incorporation. Diethylarsine, which has one H attached to the As, produces high quality GaAs but
has an inconveniently low vapor pressure. Trimethylphosphine and triethylphosphine o not pyrolyze at low enough temperatures
to be useful for conventional OMVPE growth. Tertbutylarsine (TBAs) and tertbutylphosphine (TBP) appear to be promising source
materials. TBP has a very low toxicity, a vapor pressure ideal for OMVPE growth, and the pyrolysis occurs at lower temperatures
than for PH3, allowing the use of low values of V/III ratio for the growth of high quality material. No carbon contamination can be attributed
to the TBP. Control of the As/P ratio in OMVPE grown GaAsP is much improved for TBP as compared with PH3 due to the more rapid pyrolysis. At normal growth temperatures the P distribution coefficient is nearly unity. TBAs has been
less studied, but appears to have similar attributes including a favorable vapor pressure and lower pyrolysis temperature
than AsH3, allowing OMVPE growth of GaAs at low values of V/III ratio. The substitution of TBAs for AsH3 results in no observable increase in carbon in the epitaxial GaAs. 相似文献
8.
D. P. Docter J. P. Ibbetson Y. Gao U. K. Mishra T. Liu D. E. Grider 《Journal of Electronic Materials》1998,27(5):479-483
Using secondary ion mass spectrometry (SIMS), we have investigated the excess group V content in GaAs and InP films grown
by molecular beam epitaxy at low temperature. Using the inherent depth profiling capability of SIMS, we investigated the V/III
ratio in films grown at nominally constant temperatures and also in films grown with stepped temperature profiles. Thickness
profiles of the V/III ratio show the effects of intentional temperature changes and of an unintentional drift in the actual
substrate temperature during growth. The ability to measure as little as 0.1% excess As and about 0.2% excess P indicates
excellent measurement resolution. SIMS analysis is also used to identify a narrow growth temperature range over which InP
can be grown with appreciable nonstoichiometry yet remain monocrystalline. 相似文献
9.
Warren A.C. Burroughes J.H. Woodall J.M. McInturff D.T. Hodgson R.T. Melloch M.R. 《Electron Device Letters, IEEE》1991,12(10):527-529
The fabrication of a GaAs detector which operates in the 1.3- to 1.5-μm optical range is reported. The detector is a P-i-N photodiode with an intrinsic layer composed of undoped GaAs which was grown at 225°C and subsequently annealed at 600°C. This growth process has been demonstrated to produce a high density of As precipitates in the low-temperature grown region, which the authors show to exhibit absorption through internal photoemission. The internal Schottky barrier height of the As precipitates is found to be 0.7 eV, leading to reasonable room-temperature responsivity out to around 1.7 μm 相似文献
10.
Ashish K. Verma Jay Tu J. S. Smith Hiroshi Fujioka Eicke R. Weber 《Journal of Electronic Materials》1993,22(12):1417-1420
In this work, we present electrical characterizations of n+ GaAs/low temperature (LT)-Al0.3Ga0.7As/n+ GaAs resistor structures in which the LT layers are grown at nominal substrate temperatures of 250 and 300°C. The resistivity
and Vtfl parameters of these LT-Al0.3Ga0.7As layers are compared with those of LT-GaAs and Al0.3Ga0.7As grown at a normal growth temperature of 720°C. Low-temperature Al0.3Ga0.7As layers exhibit resistivities as high as 1012 ohm-cm, nearly four orders of magnitude higher than that of LT-GaAs, and Vtfl values as high as 45 V, over twice that of LT-GaAs. We also find that the LT-Al0.3Ga0.7As materials grown at 250 and 300°C appear to show opposite and contradictory trends with respect to resistivity and Vtfl. We propose that this result can be explained by residual hopping conduction in the 250°C material. Temperature dependent
conductivity measurements confirm the presence of a hopping mechanism in LT-Al0.3Ga0.7As grown at 250°C and yield activation energies of 0.77 and 0.95 eV for LT-GaAs and LT-Al0.3Ga0.7As, respectively. 相似文献
11.
R. E. Kroon J. R. Botha J. H. Neethling T. J. Drummond 《Journal of Electronic Materials》1999,28(12):1466-1470
Degenerately doped n-type GaAs produces band-to-band luminescence with the peak energy dependent on the carrier concentration.
In this study the photoluminescence of Si-doped GaAs is examined after implantation with high energy Be ions and annealing.
The band-to-band peak energy in the unimplanted (reference) material is shown to be smaller than reported values in Te-doped
GaAs of the same carrier concentration. This is attributed to compensation in the Si doped material as a result of its amphoteric
nature. For the implanted samples, no luminescence was recorded for the unannealed samples or those annealed at 400°C and
500°C. Comparing the relative peak intensities from material annealed at 600°C for 15 min and 30 min indicates an increase
in the number of As vacancies with anneal time. For samples annealed at 700°C and 800°C, the dominant luminescence is associated
with GaAs antisite defects. It is suggested that formation of these defects occurs predominantly only at these higher temperatures.
Crystal recovery as measured by the luminescence intensity increased with both anneal temperature and time. For the implanted
sample annealed at 800°C for 15 min, the dominant peak height was 25% of that from the reference sample. 相似文献
12.
J. M. Ballingall P. Ho J. Mazurowski L. Lester K. C. Hwang J. Sutliff S. Gupta J. Whitaker 《Journal of Electronic Materials》1993,22(12):1471-1475
InxGa1−xAs (x=0.25–0.35) grown at low temperature on GaAs by molecular beam epitaxy is characterized by Hall effect, transmission
electron microscopy, and ultrafast optical testing. As with low temperature (LT) GaAs, the resistivity is generally higher
after a brief anneal at 600°C. High-resolution transmission electron microscopy shows all the as-grown epilayers to be heavily
dislocated due to the large lattice mismatch (2–3%). When the layers are annealed, in addition to the dislocations, precipitates
are also generally observed. As with LT-GaAs, the lifetime shortens as growth temperature is reduced through the range 300–120°C;
also, the lifetime in LT-InxGa1−xAs is generally shorter in as-grown samples relative to annealed samples. Metal-semiconductor-metal photodetectors fabricated
on the material exhibit response times of 1–2 picoseconds, comparable to results reported on GaAs grown at low temperature,
and the fastest ever reported in the wavelength range of 1.0–1.3 μm. 相似文献
13.
垂直梯度凝固法(VGF)生长的低位错半绝缘(SI) GaAs单晶存在电阻率和迁移率低、电学补偿度小、均匀性差等问题. 在3种不同温度条件下,对VGF-SI-GaAs晶片进行了加As压的闭管退火处理. 结果表明,经过1160℃/12h的高温退火处理后,VGF-SI-GaAs单晶的电阻率、迁移率和均匀性均得到了显著提高. 利用Hall、热激电流谱(TSC) 、红外吸收法分别测试分析了原生和退火VGF-SI-GaAs单晶样品的电学性质、深能级缺陷、EL2浓度和C浓度,并与常规液封直拉法(LEC) SI-GaAs单晶样品进行了比较. 原生VGF-SI-GaAs单晶中的EL2浓度明显低于LEC-SI-GaAs单晶,经过退火处理后其EL2浓度显著增加,电学补偿增强,而且能级较浅的一些缺陷的浓度降低,因而有效提高了其电学性能. 相似文献
14.
Current transport in molecular beam epitaxy (MBE) GaAs grown at low and intermediate growth temperatures is strongly affected
by defects. A model is developed here that shows that tunneling assisted by defect states can dominate, at some bias ranges,
current transport in Schottky contacts to unannealed GaAs material grown at the intermediate temperature range of about 400°C.
The deep defect states are modeled by quantum wells which trap electrons emitted from the cathode before re-emission to semiconductor.
Comparison of theory with experimental data shows defect states of energies about 0.5 eVbelow conduction band to provide the
best fit to data. This suggests that arsenic interstitials are likely to mediate this conduction. Comparison is also made
between as-grown material and GaAs grown at the same temperature but annealed at 600°C. It is suggested that reduction of
these defects by thermal annealing can explain lower current conduction at high biases in the annealed device as well as higher
current conduction at low biases due to higher lifetime. Quenching of current by light in the as-grown material can also be
explained based on occupancy of trap states. Identification of this mechanism can lead to its utilization in making ohmic
contacts, or its elimination by growing tunneling barrier layers. 相似文献
15.
A study concerning the effect of growth condition on As incorporation and formation of defects using transmission electron
microscopy (TEM) is presented. It is well known that devices in a narrow bandgap HgCdTe material system could suffer from
tunneling currents and generation recombination processes, especially at cryogenic temperatures, due to material defects.
For in-situ As doped p-on-n device structures grown by molecular beam epitaxy (MBE), extended defects and in particular twinning
in a p-type layer grown under Hg-rich conditions is believed to reduce the zero bias dynamic impedance of devices and significantly
impact recombination of carriers in the space charge region. Using TEM we have studied defects formed in As-doped layers grown
under Hg- and Te-rich conditions. Samples grown under high II/VI flux ratio at growth temperature of 170 C have a high density
of columnar twin defects, whereas no twin defects were seen for layers grown under optimal growth conditions at 190 C. A very
high flux of As, however, was required to incorporate As into the layers at growth temperature of 190 C. 相似文献
16.
利用气态源分子束外延技术在InP衬底上生长了包含InAlAs异变缓冲层的In0.83Ga0.17As外延层.使用不同生长温度方案生长的高铟InGaAs和InAlAs异变缓冲层的特性分别通过高分辨X射线衍射倒易空间图、原子力显微镜、光致发光和霍尔等测量手段进行了表征.结果表明, InAlAs异变缓冲层的生长温度越低, X射线衍射倒易空间图 (004) 反射面沿Qx方向的衍射峰半峰宽就越宽, 外延层和衬底之间的倾角就越大, 同时样品表面粗糙度越高.这意味着材料的缺陷增加, 弛豫不充分.对于生长在具有相同生长温度的InAlAs异变缓冲层上的In0.83Ga0.17As外延层, 采用较高的生长温度时, X射线衍射倒易空间图 (004) 反射面沿Qx方向的衍射峰半峰宽较小, 77K下有更强的光致发光, 但是表面粗糙度会有所增加.这说明生长温度提高后, 材料中的缺陷得到抑制. 相似文献
17.
Effect of As overpressure on Si-doped (111)A, (211)A and (311)A GaAs grown by molecular beam epitaxy
Si-doped (111)A, (211)A and (311)A GaAs samples grown by molecular beam epitaxy (MBE) at different As over-pressures have been studied. Hall effect measurements have revealed that the doping changes from p- to n-type when the As pressure is increased. The transition As pressure is lower for the (211)A than for the (311)A surfaces. Photo-luminescence measurements have shown that, when the As pressure is increased, arsenic vacancy defects are changed into pairs of Ga vacancy and Ga antisite defects. These results are explained by considering the orientation dependence of the surface bonding and the kinetics of the MBE growth process. 相似文献
18.
V. N. Nevedomskiy N. A. Bert V. V. Chaldyshev V. V. Preobrazhenskiy M. A. Putyato B. R. Semyagin 《Semiconductors》2014,48(11):1539-1543
Electron-microscopy studies of GaAs structures grown by the method of molecular-beam epitaxy and containing arrays of semiconductor InAs quantum dots and metallic As quantum dots are performed. An array of InAs quantum dots is formed using the Stranski-Krastanow mechanism and consists of five layers of vertically conjugated quantum dots divided by a 5-nm-thick GaAs spacer layer. The array of As quantum dots is formed in an As-enriched GaAs layer grown at a low temperature above an array of InAs quantum dots using postgrowth annealing at temperatures of 400–600°C for 15 min. It is found that, during the course of structure growth near the InAs quantum dots, misfit defects are formed; these defects are represented by 60° or edge dislocations located in the heterointerface plane of the semiconductor quantum dots and penetrating to the surface through a layer of “low-temperature” GaAs. The presence of such structural defects leads to the formation of As quantum dots in the vicinity of the middle of the InAs conjugated quantum dots beyond the layer of “low-temperature” GaAs. 相似文献
19.
J. A Carlin S. A. Ringel E. A Fitzgerald M Bulsara 《Progress in Photovoltaics: Research and Applications》2000,8(3):323-332
III–V solar cells on Si substrates are of interest for space photovoltaics since this would combine high performance space cells with a strong, lightweight and inexpensive substrate. However, the primary obstacles blocking III–V/Si cells from achieving high performance to date have been fundamental material incompatibilities, namely the 4% lattice mismatch between GaAs and Si, and the large mismatch in thermal expansion coefficient. In this paper, we report on the molecular beam epitaxial (MBE) growth and properties of GaAs layers and single junction GaAs cells on Si wafers which utilize compositionally graded GeSi intermediate buffers grown by ultra‐high vacuum chemical vapor deposition (UHVCVD) to mitigate the large lattice mismatch between GaAs and Si. GaAs cell structures were found to incorporate a threading dislocation density of 0.9–1.5×10 cm−2, identical to the underlying relaxed Ge cap of the graded buffer, via a combination of transmission electron microscopy, electron beam induced current, and etch pit density measurements. AlGaAs/GaAs double heterostructures were grown on the GeSi/Si substrates for time‐resolved photoluminescence measurements, which revealed a bulk GaAs minority carrier lifetime in excess of 10 ns, the highest lifetime ever reported for GaAs on Si. A series of growths were performed to assess the impact of a GaAs buffer layer that is typically grown on the Ge surface prior to growth of active device layers. We found that both the high lifetimes and low interface recombination velocities are maintained even after reducing the GaAs buffer to a thickness of only 0.1 μm. Secondary ion mass spectroscopy studies revealed that there is negligible cross diffusion of Ga, As and Ge at the III–V/Ge interface, identical to our earlier findings for GaAs grown on Ge wafers using MBE. This indicates that there is no need for a buffer to ‘bury’ regions of high autodoping, and that either pn or np configuration cells are easily accommodated by these substrates. Preliminary diodes and single junction AlGaAs heteroface cells were grown and fabricated on the Ge/GeSi/Si substrates for the first time. Diodes fabricated on GaAs, Ge and Ge/GeSi/Si substrates show nearly identical I–V characteristics in both forward and reverse bias regions. External quantum efficiencies of AlGaAs/GaAs cell structures grown on Ge/GeSi/Si and Ge substrates demonstrated nearly identical photoresponse, which indicates that high lifetimes, diffusion lengths and efficient minority carrier collection is maintained after complete cell processing. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
20.
D. C. Look G. D. Robinson J. R. Sizelove C. E. Stutz 《Journal of Electronic Materials》1993,22(12):1425-1428
We use the Hall effect and a new charge-transfer technique to study molecular beam epitaxial GaAs grown at the low substrate
temperatures of 300–450°C. Layers grown from 350–450°C are semi-insulating (resistivity greater than 107 Ω-cm), as grown, because of an AsGa-related donor (not EL2) at EC-0.65 eV. The donor concentrations are about 2×1018 cm−3 and 2×1017 cm−3 at growth temperatures of 300 and 400°C, respectively, and acceptor concentrations are about an order of magnitude lower.
Relatively high mobilities (∼5000 cm2/V s) along with the high resistivities make this material potentially useful for certain device applications. 相似文献