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Electrical isolation of dislocations in Ge layers on Si(001) substrates through CMOS-compatible suspended structures  [cached]
Vishal Ajit Shah, Maksym Myronov, Chalermwat Wongwanitwatana, Lewis Bawden, Martin J Prest, James S Richardson-Bullock, Stephen Rhead, Evan H C Parker, Terrance E Whall and David R Leadley
Science and Technology of Advanced Materials , 2012,
Abstract: Suspended crystalline Ge semiconductor structures are created on a Si(001) substrate by a combination of epitaxial growth and simple patterning from the front surface using anisotropic underetching. Geometric definition of the surface Ge layer gives access to a range of crystalline planes that have different etch resistance. The structures are aligned to avoid etch-resistive planes in making the suspended regions and to take advantage of these planes to retain the underlying Si to support the structures. The technique is demonstrated by forming suspended microwires, spiderwebs and van der Pauw cross structures. We finally report on the low-temperature electrical isolation of the undoped Ge layers. This novel isolation method increases the Ge resistivity to 280 Ω cm at 10 K, over two orders of magnitude above that of a bulk Ge on Si(001) layer, by removing material containing the underlying misfit dislocation network that otherwise provides the main source of electrical conduction.
Epitaxial growth of thick Ge layers with low dislocation density on silicon substrate by UHV/CVD
硅基低位错密度厚锗外延层的UHV/CVD法生长

Chen Cheng-Zhao,Zheng Yuan-Yu,Huang Shi-Hao,Li Cheng,Lai Hong-Kai,Chen Song-Yan,
陈城钊
,郑元宇,黄诗浩,李成,赖虹凯,陈松岩

物理学报 , 2012,
Abstract: Thick Ge epitaxial layers are grown on Si(001) substrates in the ultra-high vacuum chemical vapor deposition system by using the method of low temperature buffer layer combining strained layer superlattices. The microstructure and the optical properties of the Ge layers are characterized by double crystal X-ray diffraction, HRTEM, AFM and photoluminescence spectroscopy. The root-mean-square surface roughness of the Ge epilayer with a thickness of 880nm is about 0.24 nm and the full-width-at-half maximum of the Ge peak of the XRD profile is about 273". The etch pit density related to threading dislocations is less than 1.5?106 cm-2. The direct band transition photoluminescence is observed at room temperature and the photoluminescence peak is located at 1540 nm. It is indicated that the Ge epitaxial layer is of good quality and will be a promising material for Si-based optoelectronic devices
Growth of Thick Ge Epitaxial Layers with Low Dislocation Density on Silicon Substrate by UHV/CVD
UHV/CVD法生长硅基低位错密度厚锗外延层

Zhou Zhiwen,Cai Zhimeng,Zhang Yong,Cai Kunhuang,Zhou Bi,Lin Guijiang,Wang Jianyuan,Li Cheng,Lai Hongkai,Chen Songyan,Yu Jinzhong,Wang Qiming,
周志文
,蔡志猛,张永,蔡坤煌,周笔,林桂江,汪建元,李成,赖虹凯,陈松岩,余金中,王启明

半导体学报 , 2008,
Abstract: Thick Ge epitaxial layers are grown on Si(001) substrates with low temperature buffer layers with ultra-high vacuum chemical vapor deposition systems using Si2H6 and GeH4 as precursors.The deposition process of the Ge layer on Si is investigated in real time by reflection high-energy electron diffraction, and the quality of the Ge layer was evaluated by atomic force microscopy, double crystal X-ray diffraction (XRD), and Raman measurement.The root-mean-square surface roughness of the Ge epilayer with a thickness of 550nm is less than 1nm and the full-width-at-half maximum of the Ge peak of the XRD profile and the Ge-Ge mode of the Raman spectra are about 530" and 5.5cm-1, respectively.These measurements indicate that the Ge epitaxial layer is of good quality.The etch pit density related to threading dislocations is less than 5e5cm-2.This is a promising material for Si-based long wavelength photodetectors and electronic devices
Non-contact monitoring of Ge and B diffusion in B-doped epitaxial Si1-xGex bi-layers on silicon substrates during rapid thermal annealing by multiwavelength Raman spectroscopy
Min-Hao Hong,Chun-Wei Chang,Dung-Ching Perng,Kuan-Ching Lee
AIP Advances , 2012, DOI: 10.1063/1.4748294
Abstract: B-doped, thin Si1-xGex bi-layers with different Ge content and B concentrations were epitaxially grown on Si(100) device wafers. Diffusion behavior of Ge and B atoms during rapid thermal annealing were monitored by multiwavelength micro-Raman spectroscopy. Raman spectra indicating possible Ge and B redistribution by thermal diffusion was observed from B-doped, thin Si1-xGex bi-layers on Si(100) wafers after rapid thermal annealing at 950°C or higher. Significant Ge and B diffusion in Si1-xGex bi-layers and Si substrates was verified by secondary ion mass spectroscopy. Pile up of B atoms at the surface and at the boundary between Si1-xGex bi-layers was observed in the early stages of thermal diffusion.
Effect of interface roughness on the carrier transport in germanium MOSFETs investigated by Monte Carlo method

Du Gang,Liu Xiao-Yan,Xia Zhi-Liang,Yang Jing-Feng,Han Ru-Qi,

中国物理 B , 2010,
Abstract: Interface roughness strongly influences the performance of germanium metal--organic--semiconductor field effect transistors (MOSFETs). In this paper, a 2D full-band Monte Carlo simulator is used to study the impact of interface roughness scattering on electron and hole transport properties in long- and short- channel Ge MOSFETs inversion layers. The carrier effective mobility in the channel of Ge MOSFETs and the in non-equilibrium transport properties are investigated. Results show that both electron and hole mobility are strongly influenced by interface roughness scattering. The output curves for 50~nm channel-length double gate n and p Ge MOSFET show that the drive currents of n- and p-Ge MOSFETs have significant improvement compared with that of Si n- and p-MOSFETs with smooth interface between channel and gate dielectric. The $82\%$ and $96\%$ drive current enhancement are obtained for the n- and p-MOSFETs with the completely smooth interface. However, the enhancement decreases sharply with the increase of interface roughness. With the very rough interface, the drive currents of Ge MOSFETs are even less than that of Si MOSFETs. Moreover, the significant velocity overshoot also has been found in Ge MOSFETs.
Simulation Study of Ge p-type Nanowire Schottky Barrier MOSFETs  [PDF]
Jaehyun Lee,Mincheol Shin
Physics , 2013, DOI: 10.1109/LED.2012.2237375
Abstract: Ambipolar currents in Germanium p-type nanowire Schottky barrier MOSFETs were calculated fully quantum-mechanically by using the multi-band k.p method and the non-equilibrium Green's function approach. We investigated the performance of devices with 100, 110, and 111 channel orientations, respectively, by varying the nanowire width, Schottky barrier height, and EOT. The 111 oriented devices showed the best performance. In comparison to Si as a channel material, Ge is more desirable because more current can be injected into the channel, resulting in steeper subthreshold slope and higher on-state current. Our calculations predict that the Ge channel devices should have an EOT gain of 0.2-0.5 nm over Si channel devices.
Surface instability and dislocation nucleation in strained epitaxial layers
Trushin, O.;Granato, E.;Ying, S.C.;Kosterlitz, J.M.;Ala-Nissila, T.;Salo, P.;
Brazilian Journal of Physics , 2002, DOI: 10.1590/S0103-97332002000200034
Abstract: we have studied numerically the stability and defect nucleation in epitaxial layers on a substrate with lattice mismatch. stress relaxation and energy barriers for misfit dislocation nucleation are estimated using modern methods for saddle point search based on a combination of activation with local repulsive potential and the nudged elastic band method. stress relaxation processes correspond to different transition paths from coherent to incoherent states of the epitaxial layer.using a two-dimensional atomistic model with lennard-jones interacting potential, we and different equilibrium critical thickness and activation energy behavior for dislocation nucleation of epitaxial films under tensile and compressive strain. for tensile strain, the energy barrier decreases with thickness while it reaches a constant value for compressive strain.
Surface instability and dislocation nucleation in strained epitaxial layers  [cached]
Trushin O.,Granato E.,Ying S.C.,Kosterlitz J.M.
Brazilian Journal of Physics , 2002,
Abstract: We have studied numerically the stability and defect nucleation in epitaxial layers on a substrate with lattice mismatch. Stress relaxation and energy barriers for misfit dislocation nucleation are estimated using modern methods for saddle point search based on a combination of activation with local repulsive potential and the Nudged Elastic Band method. Stress relaxation processes correspond to different transition paths from coherent to incoherent states of the epitaxial layer.Using a two-dimensional atomistic model with Lennard-Jones interacting potential, we and different equilibrium critical thickness and activation energy behavior for dislocation nucleation of epitaxial films under tensile and compressive strain. For tensile strain, the energy barrier decreases with thickness while it reaches a constant value for compressive strain.
Luminescence and deep-level transient spectroscopy of grown dislocation-rich Si layers
I. I. Kurkina,I. V. Antonova,A. A. Shklyaev,S. A. Smagulova
AIP Advances , 2012, DOI: 10.1063/1.4748863
Abstract: The charge deep-level transient spectroscopy (Q-DLTS) is applied to the study of the dislocation-rich Si layers grown on a surface composed of dense arrays of Ge islands prepared on the oxidized Si surface. This provides revealing three deep-level bands located at EV + 0.31 eV, EC – 0.35 eV and EC – 0.43 eV using the stripe-shaped p-i-n diodes fabricated on the basis of these layers. The most interesting observation is the local state recharging process which proceeds with low activation energy (~50 meV) or without activation. The recharging may occur by carrier tunneling within deep-level bands owing to the high dislocation density ~ 1011 - 1012 cm-2. This result is in favor of the suggestion on the presence of carrier transport between the deep states, which was previously derived from the excitation dependence of photoluminescence (PL) intensity. Electroluminescence (EL) spectra measured from the stripe edge of the same diodes contain two peaks centered near 1.32 and 1.55 μm. Comparison with PL spectra indicates that the EL peaks are generated from arsenic-contaminated and pure areas of the layers, respectively.
Amorphous carbon layers on polymeric substrates  [PDF]
R.M. Nowak,S. Jonas,S. Zimowski,K. Tkacz-?miech
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: urpose: This paper is aimed to study an effect of nitrogen incorporation on the structure and tribological properties of amorphous a C:N:H layers grown on polycarbonate substrates.Design/methodology/approach: Series of the layers were deposited from CH4 + N2 gas mixture with application of Plasma Enhanced Chemical Vapour Deposition technique assisted by radio waves (RF PE CVD). An analysis of atomic-level structure of the layers was made using FT IR technique. The samples were subjected to investigations of friction coefficient and wear resistance. The respective measurements were performed using Micro-Combi-Tester and a tribometer in ball-on-disc configuration.Findings: The IR spectra of the obtained layers have demonstrated a presence of nitrogen bonded both to carbon and to hydrogen. A formation of the following bonds has been confirmed: -C≡N, -NH2, -C-NH2, >C=NH. All they are typical for a-C:N:H layers. The tribological tests have shown that the layers reduce the friction coefficient of the polycarbonate (up to 50 %) and considerably improve abrasion resistance.Research limitations/implications: Further studies in order to find relations between growing conditions and the properties of the layers should be performed. A role of the chemical composition and structure should be carefully analyzed.Practical implications: An application of carbon overcoats on polycarbonates may improve the usable properties of plastic components (hardness, scratch resistance, UV radiation resistance). This will make polycarbonates attractive materials of wide spectrum of possible applications.Originality/value: It has been shown in this research that application of RF PE CVD technique allows obtaining the a-C:N:H layers improving usable properties of plastics. The layers well adhesive to the substrate may be obtained at the temperatures below 80oC.
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