共查询到20条相似文献,搜索用时 0 毫秒
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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
3.
R. S. Berg Nergis Mavalvala Tracie Steinberg F. W. Smith 《Journal of Electronic Materials》1990,19(11):1323-1330
Raman scattering measurements on high-resistivity layers of GaAs grown by molecular beam epitaxy at low temperature are presented.
Several defect-related features are ob-served, including two peaks attributed to quasi-localized vibrational modes of point
de-fects, one with a frequency of 223 cm−1 similar to a mode previously observed in elec-tron-irradiated GaAs, and the other with a frequency of 47 cm−1 similar to a mode observed in ion-implanted GaAs. We suggest that these are due to arsenic interstitials and gallium vacancies,
respectively. We also observe peaks at 200 and 258 cm−1, which we believe may be due to vibrational modes in small clusters of arsenic. The 223 cm−1 mode is the only defect-related mode still observed after a 10-min annealing treatment at 600° C, although it is significantly
broader and has different symmetry from the 223 cm−1 mode in the unannealed material. This indicates that the 223 cm−1 mode in the annealed material is due, at least in part, to a defect other than the arsenic interstitial. 相似文献
4.
Fangxing Zha Qiuying Zhang Haoguang Dai Xiaolei Zhang Li Yue Shumin Wang Jun Shao 《半导体学报》2021,42(9):31-35
The ultrahigh vacuum scanning tunneling microscope (STM) was used to characterize the GaSb1-xBix films of a few nanometers thickness grown by the molecular beam epitaxy (MBE) on the GaSb buffer layer of 100 nm with the GaSb (100) sub-strates.The thickness of the GaSb1-xBix layers of the samples are 5 and 10 nm,respectively.For comparison,the GaSb buffer was also characterized and its STM image displays terraces whose surfaces are basically atomically flat and their roughness is generally less than 1 monolayer (ML).The surface of 5 nm GaSb1-xBix film reserves the same terraced morphology as the buffer layer.In contrast,the morphology of the 10 nm GaSb1-xBix film changes to the mound-like island structures with a height of a few MLs.The result implies the growth mode transition from the two-dimensional mode as displayed by the 5 nm film to the Stranski-Krastinov mode as displayed by the 10 nm film.The statistical analysis with the scanning tunneling spectroscopy (STS)measurements indicates that both the incorporation and the inhomogeneity of Bi atoms increase with the thickness of the GaSb1-xBix layer. 相似文献
5.
A. Srinivasan K. Sadra J. C. Campbell B. G. Streetman 《Journal of Electronic Materials》1993,22(12):1457-1459
We report a study of the sub-bandgap photoresponse of p-i-n photodetectors with 1 μm low-temperature intrinsic layers, and
its dependence on the growth temperature of the intrinsic layer. Diodes with intrinsic layers grown near 250°C exhibit the
highest photoresponse. The photoresponse decreases gradually as the growth temperature is raised above 250°C. For growth temperatures
at or below 200°C, a drastic drop in the photoresponse is observed, along with degradation of crystal quality in the material.
The extracted internal Schottky barrier heights are found to be within the range 0.7–0.8 eV. 相似文献
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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
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Low temperature (LT-) grown GaAs has been used as a dielectric in a metal/ dielectric/semiconductor structure, and its capacitance
behavior has been investigated by C–VB} and admittance spectroscopy. The C-VB} measurement revealed a barrier height of 0.40 eV at the interface of the LT- and n-GaAs. The capacitance-temperature profile
shows a step decrease in capacitance, accompanied by a maximum conductance as the measurement temperature was decreased. The
detailed investigation shows that this anomalous C–T behavior is caused by the increase of resistivity of the LT-GaAs, which
leads to the formation of a metal/insulator/semiconductor structure at low temperature. This result has an impact on the application
of the LT-GaAs, because it introduces a frequency dispersion to the device characteristics. 相似文献
10.
Electrical properties of low-temperature GaAs grown by molecular beam epitaxy and migration enhanced epitaxy 总被引:1,自引:0,他引:1
Measurements on low-temperature GaAs epitaxial layers (LT-GaAs) grown by molecular beam epitaxy and migration enhanced epitaxy
showed that the excess arsenic incorporated during growth played a crucial role in determining their electrical properties.
The electrical transport in LT-GaAs grown by a standard molecular beam epitaxy proceeded mainly via a hopping process, which
showed a higher activation energy and onset temperature than those usually observed in lightly doped semiconductors. Using
migration enhanced epitaxy to grow LT-GaAs, we were able to substantially reduce the density of As-rich defects and to achieve
a good Hall mobility in Be-doped LT-GaAs. The study presented here indicates that, with controlled excess arsenic incorporation
during growth, LT-GaAs can vary in a range of conduction properties and thus can be engineered for different device applications. 相似文献
11.
C. S. Kyono B. Tadayon M. E. Twigg A. Giordana D. S. Simons M. Fatemi S. Tadayon 《Journal of Electronic Materials》1993,22(12):1437-1440
The effect of annealing on the electrical properties of a GaAs diode structure, which incorporated a nominally undoped low-temperature
(LT) layer on top of conventionally grown p-type GaAs, is examined. Unannealed GaAs grown by molecular beam epitaxy at substrate
temperatures below 250°C is amorphous and highly resistive. Annealing at high temperatures converts the undoped LT-GaAs from
amorphous to single crystal material. The annealed material is n-type. The current-voltage characteristics of the LT on p-type
GaAs structures showed greater asymmetry, with lower reverse leakage currents, as the anneal temperature was increased above
400°C. This reflects the improved crystal quality of the LT layer. 相似文献
12.
p-nitrobenzonitrile纳米有机薄膜的超高密度信息存储研究 总被引:2,自引:0,他引:2
采用扫描隧道显微镜(STM)在p-nitrobenzonitrile(PNBN)单体有机薄膜上进行信息记录点的写入研究。通过在STM针尖和高定向裂解石墨(HOPG)衬底之间施加一系列的电压脉冲进行信息记录点的写入,得到了一个信息点点径小于1nm,对应存储密度高达10^13 bit/cm^2的信息存储点阵,电流-电压(I-V)曲线表明,薄膜上非信息点存储区域是高电阻区,而信息点存储区域是导电区,具有0-1信息存储特性,PNBN单体有机薄膜的存储机制可能是规则排列的PNBN分子在强电场作用下由有序向无序的转变,使得薄膜的电阻由高阻态向低阻态转变,从而实现信息点的写入。 相似文献
13.
超高真空扫描隧道谱实验对碲镉汞室温带隙的直接测定 总被引:1,自引:0,他引:1
利用超高真空扫描隧道显微镜的隧道谱实验对汞空位掺杂的液相外延P型碲镉汞材料在室温条件下进行测量,发现直接的电流-电压隧道谱对带隙预言一定程度上要受到成像偏置电压的影响.但当采用了锁相放大测量技术,通过实验直接获取微分隧道谱(dI/dV)信号,并利用电流-电压谱对dI/dV作归一化处理时,最终结果则能较准确、可靠地预言材料的带隙,表明扫描隧道谱方法作为独立于光学方法之外的另一种实验表征手段对碲镉汞能带电子结构研究的适用性. 相似文献
14.
本工作应用截面扫描隧道显微镜(XSTM)研究了分子束外延生长的Hg0.72Cd0.28Te薄膜。扫描隧道谱(STS)测量显示, 此碲镉汞材料的电流-电压(I/V)隧道谱呈现的零电流平台宽度(隧道谱表观带隙)比其实际材料带隙增大约130%,说明存在明显的针尖诱导能带弯曲(TIBB)效应。应用扫描隧道谱三维TIBB模型计算发现低成像偏压测量时获取的I/V隧道谱数据与理论计算结果有令人满意的一致性。然而较大成像偏压时所计算的I/V谱与实验谱线在较大正偏压区域存在一定偏离。这是由于目前的TIBB模型未考虑带带隧穿,缺陷辅助隧穿等碲镉汞本身的输运机制对隧道电流的影响造成的。 相似文献
15.
扫描隧道显微镜是一种分辨率极高的表面研究仪器,针尖对其工作过程及图像质量有决定性的影响。本文针对目前针尖腐蚀成功率较低和不稳定的缺点,提出了一种新的电路。该设计改变了反应电流的测量机制,使实际反应电压在实验过程中保持稳定,同时为了得到更加尖锐的针尖,利用差分电路监控反应过程的电流变化,能够在反应结束的瞬间立刻切断电路,避免了过度反应使针尖变钝。最后,通过观察反应电压,阴极圆环位置,差分电路灵敏度以及电解液浓度对针尖质量的影响,给出了合适的反应参数,并且比较了差分电路和传统电流阈值监控法的优缺点。结果表明新电路在稳定性上有所提高,与电流阈值监控法相比,针尖质量更好,另外扫描隧道显微镜测试结果也表明针尖质量完全符合要求。 相似文献
16.
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
17.
Hall and drift mobilities in molecular beam epitaxial grown GaAs 总被引:1,自引:0,他引:1
V. W. L. Chin T. Osotchan M. R. Vaughan T. L. Tansley G. J. Griffiths Z. Kachwalla 《Journal of Electronic Materials》1993,22(11):1317-1321
A series of nominally undoped and Si-doped GaAs samples have been grown by molecular beam epitaxy (MBE) with Hall concentrations
ranging from 1015 to 1019 cm−3 and mobilities measured at 77 and 300K by Hall-van der Pauw methods. Drift mobilities were calculated using the variational
principle method and Hall scattering factors obtained from a relaxation-time approximation to permit cross-correlation of
experimental data with drift or Hall mobilities and actual or Hall electron concentrations. At 77K, both high purity and heavily
doped samples are well represented by either drift or Hall values since piezoelectric acoustic phonon scattering and strongly
screened ionized impurity scattering hold the Hall factor close to unity in the respective regimes. Between n≊1015 and 1017 cm−3, where lightly screened ionized impority scattering predominates, Hall mobility overestimates drift mobility by up to 50
percent and Hall concentration similarly underestimates n. At 300K, polar optical phonons limit mobility and a Hall factor
up to 1.4 is found in the lowest doped material, falling close to unity above about 1016 cm−3. Our calculation also agrees remarkably well with the Hall mobility of the highest purity MBE grown sample reported to date. 相似文献
18.
Based on micrographic as well as experimental analyses, we show that particulates which inadvertently adhere to the surface
before the wafer is ready for growth are one of the most significant origins for the formation of oval defects on the GaAs
layers grown by molecular beam epitaxy. We show that the density of surface particulates is proportional to that of airborne
particles surrounding the wafer under preparation, especially during the drying and transferring process. With reduction of
airborne particles, we simultaneously reduce the density of oval defects from a few thousand to about 200 cm-2 for 1-μm thick layers. 相似文献
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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