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1.
《Microelectronics Journal》2007,38(6-7):800-804
The 20-nm-thick Si cap layer/74-nm-thick Si0.72Ge0.28 epilayer/Si heterostructures implanted by 25 keV H+ ion to a dose of 1×1016 cm−2 were annealed in ultra-high vacuum ambient and dry O2 ambient at the temperature of 800 °C for 30 min, respectively. Rutherford backscattering/ion channeling (RBS/C), Raman spectra, high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) were used to characterize the structural characteristics of the Si0.72Ge0.28 layer. Investigations by RBS/C demonstrated that the crystal quality of the Si/Si0.72Ge0.28/Si heterostructure sample implanted by 25 keV H+ in conjunction with subsequent annealing in dry O2 ambient is superior to that of identical sample annealing in ultra-high vacuum ambient. The less strain relaxation of SiGe layer of the Si/Si0.72Ge0.28/Si heterostructures implanted by H ion and annealed in dry O2 ambient at the temperature of 800 °C for 30 min could be doublechecked by Raman spectra as well as HRXRD, which was compared with that in an identical sample annealed in ultra-high vacuum ambient for identical thermal budget. In addition, the SiGe layer of the H-implanted Si/SiGe/Si heterostructural sample annealed in dry O2 ambient accompanied by better crystal quality and less strain relaxation made its surface morphology superior to that of the sample annealed in ultra-high vacuum ambient at the temperature of 800 °C for 30 min, which was also verified by AFM images.  相似文献   

2.
The work addresses the occurrence of Ge dangling bond type point defects at GexSi1?x/insulator interfaces as evidenced by conventional electron spin resonance (ESR) spectroscopy. Using multifrequency ESR, we report on the observation and characterization of a first nontrigonal Ge dangling bond (DB)-type interface defect in SiO2/(1 0 0)GexSi1?x/SiO2/(1 0 0)Si heterostructures (0.27 ? x ? 0.93) manufactured by the condensation technique, a selective oxidation method enabling Ge enrichment of a buried epitaxial Si-rich SiGe layer. The center, exhibiting monoclinic-I (C2v) symmetry is observed in highest densities of ~7 × 1012 cm?2 of GexSi1?x/SiO2 interface for x  0.7, to disappear for x outside the ]0.45–0.87[ interval, with remarkably no copresence of Si Pb-type centers. Neither are trigonal Ge DB centers observed, enabling unequivocal spectral analysis. Initial study of the defect passivation under annealing in molecular H2 has been carried out. On the basis of all data the defect is depicted as a Ge Pb1-type center, i.e., distinct from a trigonal basic Ge Pb(0)-type center (Ge3Ge). The modalities of the defect’s occurrence as unique interface mismatch healing defect is discussed, which may widen our understanding of interfacial DB centers in general.  相似文献   

3.
B-doped Si0.77Ge0.23 of various surface-doping levels was used to investigate the evolution of implant damage and the corresponding transient enhanced diffusion of boron as a function of boron concentration. These layers were implanted with a non-amorphizing 60 keV, 1×1014 cm−2 Si, and annealed at 750 °C. Plan-view transmission electron microscopy (PTEM) confirmed the formation and dissolution of dislocation loops. Transient enhanced diffusion (TED) is evident in the surface doped SiGe, but the low diffusivity of interstitials in Si0.77Ge0.23 and the presence of interstitial traps inhibited TED at the deeper B marker layer.  相似文献   

4.
By using our low-energy Ar plasma enhanced chemical vapor deposition (CVD) at a substrate temperature below 100 °C during plasma exposure without substrate heating, modulation of valence band structures and infrared photoluminescence can be observed by change of strain in a Si/strained Si0.4Ge0.6/Si(100) heterostructure. For the strained Si0.5Ge0.5 film, Hall mobility at room temperature was confirmed to be as high as 660 cm2 V−1 s−1 with a carrier concentration of 1.3×1018 cm−3 for n-type carrier, although the carrier origin was unclear. Moreover, good rectifying characteristics were obtained for a p+Si/nSi0.5Ge0.5 heterojunction diode. This indicates that the strained Si-Ge alloy and Si films and their heterostructures epitaxially grown by our low-energy Ar plasma enhanced CVD without substrate heating can be applicable effectively for various semiconductor devices utilizing high carrier mobility, built-in potential by doping and band engineering.  相似文献   

5.
We have investigated the Si0.8Ge0.2/Si multi-layer grown directly onto the Si (001) substrates using reduced pressure chemical vapor deposition. The thicknesses of the Si0.8Ge0.2/Si multi-layer were determined using transmission electron microscopy. From the results of energy-dispersive X-ray spectroscopy and X-ray diffraction analyses on the Si0.8Ge0.2/Si multi-layer, Ge composition in the Si1?xGex layers was determined as ~20% and the value of residual strain ε of the Si0.8Ge0.2 layer is calculated to be 0.012. Three peaks are observed in Raman spectrum, which are located at approximately 514, 404, and 303 cm?1, corresponding to the vibration of Si–Si, Si–Ge, and Ge–Ge phonons, respectively. The photoluminescence spectrum originates from the radiative recombinations both from the Si substrate and the Si0.8Ge0.2/Si multi-layer. For the Si0.8Ge0.2/Si multi-layer, the transition peaks related to the quantum well region observed in the photocurrent spectrum were preliminarily assigned to e–hh and e–lh fundamental excitonic transitions.  相似文献   

6.
Low-temperature (∼400 °C) metal-induced crystallization of hydrogenated amorphous Si0.5Ge0.5 thin films using Au solution has been investigated by X-ray diffraction, Raman spectra, scanning electron microscopy and atomic force microscopy. It was shown that Au solution significantly promotes the crystallization of the films at low temperatures. The effects of annealing temperature and concentration of the Au solution on the structure and morphology of the films were analyzed. The increase in crystallinity was observed with increasing the annealing temperature. The Raman shifts of Ge–Ge and Si–Ge peaks with the annealing temperature were also discussed.  相似文献   

7.
Hole resonant-tunneling diodes (RTD) with Si/strained Si1?xGex heterostructures epitaxially grown on Si(1 0 0) have been fabricated and improvement in negative differential conductance (NDC) characteristics for high Ge fraction such as x = 0.5 was investigated. It is clearly shown that SiH4 exposure at low temperatures of 400–450 °C just after Si1?xGex epitaxial growth is effective to suppress surface roughness in atomic order. In the case of the RTD with x = 0.48, NDC characteristics for 1.4-nm thick Si barriers were observed at higher temperatures around 270 K than that for 2.4-nm thick Si barriers. By increasing the Ge fraction to x = 0.58, NDC characteristics were also observed at higher temperatures around 290 K than that with x = 0.48.  相似文献   

8.
Experiments on the diffusion of Si and Ge in Si1-xGex-isotope heterostructures with Ge contents x=0, 0.05, and 0.25 were performed at temperatures between 870 and . The concentration profiles of the stable Si- and Ge-isotopes were recorded by means of time-of-flight secondary ion mass spectrometry. For all compositions, an Arrhenius type temperature dependence of diffusion was observed. The activation enthalpy of Si diffusion in SiGe equals the activation enthalpy of Ge diffusion and the pre-exponential factors agree within experimental accuracy. However, the absolute values of the Si and Ge diffusion coefficients indicate a clear trend. In elemental Si the diffusion coefficients of Si and Ge agree, but the difference between the diffusion coefficients of Ge and Si in Si1-xGex increases with x. This indicates that with increasing Ge content the diffusional jumps of Ge atoms become more successful compared to that of Si. This trend is explained with an increasing contribution of vacancies to self-diffusion in Si1-xGex with an increase of the Ge content x.  相似文献   

9.
The authors have identified oxidation and desorption processes of Ge native oxide by chemical bonding states measured by X-ray photoemission spectroscopy. Ge oxidation occurs at the temperatures of 450–500 °C in an oxidizing ambient. Ge desorption in nitrogen ambient is observed at the temperatures of 500–550 °C, which is higher than the oxidation temperature by 50 °C. Combined oxidation and desorption processes proceed subsequently and cause a loss of Ge from the surface when Ge is annealed in oxidizing ambient at a temperature higher than desorption temperature. The surface loss is avoided when Ge is annealed with SiO2 cap layer in an identical annealing condition.  相似文献   

10.
CMOS-compatible low-temperature formation of self-assembled Ge quantum dots (QDs) by carbon (C) mediation via a solid-phase epitaxy (SPE) has been demonstrated. The samples were prepared by a solid-source molecular beam epitaxy (MBE) system. C and Ge were successively deposited on Si(100) at 200 °C and Ge/C/Si heterostructure was annealed in the MBE chamber. Sparse Volmer-Weber mode Ge dots without a wetting layer were formed for C coverage (θC) of 0.25 and 0.5 ML by lowering SPE temperature (TS) to 450 °C, but small and dense Stranski-Krastanov (SK)-mode Ge QDs with the wetting layer were obtained with increasing C coverage of 0.75 ML even at 450 °C. From the investigation of SPE temperature effect on Ge QD formation for θC of 0.75 ML, SK-mode Ge QDs of about 10 nm in diameter and of about 4.5×1011 cm−2 in density were formed at TS≥400 °C. The wetting layer of SK-mode QDs was almost constant 0.2-nm thick at TS≥450 °C. Measurements of chemical binding states of C in Ge QDs and at Ge/Si interface revealed that a large amount of C–Ge bonds were formed in the wetting layer for high C coverage, and the formation of C–Ge bonds, together with the formation of C–Si bonds, enabled the low-temperature formation of small and dense Ge QDs. These results suggest that the C-mediated solid-phase epitaxy is effective to form small and dense SK-mode QDs at low temperature.  相似文献   

11.
Structural and electrical properties of ALD-grown 5 and 7 nm-thick Al2O3 layers before and after implantation of Ge ions (1 keV, 0.5–1 × 1016 cm?2) and thermal annealing at temperatures in the 700–1050 °C range are reported. Transmission Electron Microscopy reveals the development of a 1 nm-thick SiO2-rich layer at the Al2O3/Si substrate interface as well as the formation of Ge nanocrystals with a mean diameter of ~5 nm inside the implanted Al2O3 layers after annealing at 800 °C for 20 min. Electrical measurements performed on metal–insulator–semiconductor capacitors using Ge-implanted and annealed Al2O3 layers reveal charge storage at low-electric fields mainly due to location of the Ge nanocrystals at a tunnelling distance from the substrate and their spatial dispersion inside the Al2O3 layers.  相似文献   

12.
The reaction of cobalt with the Si-sacrificial cap in the strained Si/Si1−xGex/Si MBE grown heterostructure was studied. The Si-cap is added to prevent the relaxation of the SiGe and to guarantee uniform and reliable silicidation reaction. The Si1−xGex epilayer, with Ge content between 18 and 28 at%, was highly B doped, while the Si-cap was undoped or B doped either during growth or by ion implantation. Cobalt evaporation was followed by rapid thermal annealing at 450–700°C for 30 sec in N2 or Ar+10%H2. When the silicide penetrated the Si-cap/Si1−xGex interface, noticeable out-diffusion of Ge and B to the surface was observed. In spite of the presence of the Si-cap significant strain relaxation was observed in three cases: (1) in the implanted samples, although the implantation was confined to the Si-cap, (2) when the Co layer was too thick, such that the silicide penetrated the SiGe layer and (3) when the Ge content in the SiGe layer was relatively high (27.5%).  相似文献   

13.
A SiGe-buffer structure for growth of high-quality GaAs layers on a Si (100) substrate is proposed. For the growth of this SiGe-buffer structure, a 0.8-μm Si0.1 Ge0.9 layer was first grown. Because of the large mismatch between this layer and the Si substrate, many dislocations formed near the interface and in the low part of the Si0.1Ge0.9 layer. A 0.8-μm Si0.05Ge0.95 layer and a 1-μm top Ge layer were subsequently grown. The strained Si0.05Ge0.95/Si0.1Ge0.9 and Ge/Si0.05Ge0.95 interfaces formed can bend and terminate the upward-propagated dislocations very effectively. An in-situ annealing process is also performed for each individual layer. Finally, a 1–3-μm GaAs film was grown by metal-organic chemical vapor deposition (MOCVD) at 600°C. The experimental results show that the dislocation density in the top Ge and GaAs layers can be greatly reduced, and the surface was kept very smooth after growth, while the total thickness of the structure was only 5.1 μm (2.6-μm SiGe-buffer structure +2.5-μm GaAs layer).  相似文献   

14.
This study investigates the properties of high Ge content silicon-germanium thin films in the non-hydrogenated state (Ge-rich SiGe) deposited on glass by RF magnetron co-sputtering in both in-situ and ex-situ solid phase crystallization (SPC) at various temperatures, such as RT to 550 °C. The structural and optical characteristics of SiGe films have been explored systematically by optimizing growth temperature. Atomic composition of films was determined by EDX, which showed up to 77 at% of Ge. Structural properties were characterized by XRD, which revealed all samples to be in amorphous nature. The results from Raman and UV–VIS–IR transmittance measurements showed that the properties of amorphous Si0.23Ge0.77 films improved at 450 °C in both in-situ and ex-situ SPC processes. In addition, EDX exposed an advantage of in-situ process over ex-situ due to the incorporation of oxygen during ex-situ thermal annealing. Possible deposition at low substrate temperature as found here suggests that these Si0.23Ge0.77 films have a substantial potential to be used in thin film Si-based solar cells.  相似文献   

15.
We examined the effects of post-annealing in forming-gas ambient on the spin-on-dielectric (SOD)-buffered passivation as well as the conventional plasma-enhanced chemical vapor deposition (PECVD) Si3N4 passivation structure in association with the quantitative analysis of defects at the passivation interfaces of AlGaN/GaN high electron mobility transistors (HEMTs). Before the annealing, the interface state densities (Dit) of the PECVD Si3N4 are one-order higher (1012–1013 cm−2 eV−1) than those of the SOD SiOx (1011–1012 cm−2 eV−1) as derived from CV characterization. Clear reduction in Dit from the PECVD Si3N4 is extracted to a level of 1011–1012 cm−2 eV−1 with a stronger absorption from Si–N peak in Fourier transform infrared spectroscopy spectra after the post-annealing. On the other hand, negligible difference in Dit value is obtained from the SOD SiOx. In this paper we propose that much lower measurement levels (~156 mA/mm) before the annealing and substantial recovery (~13% increase) after the annealing in maximum drain current density of the AlGaN/GaN HEMTs with Si3N4 passivations are due to the original higher density before the annealing and greater reduction in Dit of the PECVD Si3N4 after the annealing. Significant reduction after the annealing in gate–drain leakage current (from ~10−3 to ~10−5 A, 100-μm gate width) of the HEMTs with the Si3N4 passivation is also supposed to be attributed to the reduction of Dit.  相似文献   

16.
2000 Å-SiO2/Si(1 0 0) and 560 Å-Si3N4/Si(1 0 0) wafers, that are 10 cm in diameter, were directly bonded using a rapid thermal annealing method, so-called fast linear annealing (FLA), in which two wafers scanned with a high-power halogen lamp. It was demonstrated that at lamp power of 550 W, corresponding to the surface temperature of ∼450°C, the measured bonded area was close to 100%. At the same lamp power, the bond strength of the SiO2∥Si3N4 wafer pair reached 2500 mJ/m2, which was attained only above 1000°C with conventional furnace annealing for 2 h. The results clearly show that the FLA method is far superior in producing high-quality directly bonded Si wafer pairs with SiO2 and Si3N4 films (Si/SiO2∥Si3N4/Si) compared to the conventional method.  相似文献   

17.
The influence of crystallinity of as-deposited Ge films on Ge quantum dot (QD) formation via carbon (C)-mediated solid-phase epitaxy (SPE) was investigated. The samples were fabricated by solid-source molecular beam epitaxy (MBE). Ge/C/Si structure was formed by sequential deposition of C and Ge at deposition temperature (TD) of 150–400 °C, and it was heat-treated in the MBE chamber at 650 °C. In the case of amorphous or a mixture of amorphous and nano-crystalline Ge film grown for TD ≤250 °C, density of QDs increased with increasing TD due to the increase of C-Ge bonds in Ge layer. Ge QDs with diameter of 9.2±2.1 nm were formed in the highest density of 8.3×1011 cm−2 for TD =250 °C. On the contrary, in the case of polycrystalline Ge film for TD ≥300 °C, density of QDs decreased slightly. This is because C incorporation into Ge layer during SPE was suppressed due to the as-crystallized columnar grains. These results suggest that as-deposited Ge film in a mixture of amorphous and nano-crystalline state is suitable to form small and dense Ge QDs via C-mediated SPE.  相似文献   

18.
19.
Si1−xGex bulk crystals (0.2<x<0.85) with various B doping levels were grown by the traveling liquidus zone (TLZ) method for fabricating substrates of high mobility electronic devices. Large single crystals with a diameter ranging from 30 to 50 mm were achieved. Si1−xGex crystals were characterized by measuring concentration profile along and perpendicular to the growth axis, indicating good compositional homogeneity. High crystalline quality was evaluated by electron backscatter spectroscopy and X-ray diffraction. Measured hole mobility was higher than the previously reported data for the similar dopant concentration and Ge content, suggesting smaller alloy scattering effects and high crystalline nature in the TLZ-grown Si1−xGex bulk crystals.  相似文献   

20.
Phase Change Memory (PCM) operation relies on the reversible transition between two stable states (amorphous and crystalline) of a chalcogenide material, mainly of composition Ge2Sb2Te5 (GST). In Wall type PCM cells, cycling endurance induces a gradual change of the cell electrical parameters caused by variations in the chemical composition of the active volume. The region closer to the GST-heater contact area, becomes more Sb rich and Ge depleted. The new alloy has usually different thermal characteristics for the phase transitions that influence the electrical behavior of the cell. In this study we analyze the morphological, structural and electrical properties of two Sb-rich non-stoichiometric alloys: Ge14Sb35Te51 and Ge14Sb49Te37, at their amorphous and crystalline phase. Experiments have been performed in non-patterned blanket films and, to simulate the device size, in amorphous regions of 20 nm, 50 nm and 100 nm diameter respectively. The amorphous Ge14Sb35Te51 film crystallizes in the meta-stable face centered cubic structure at 150 °C and in the rhombohedral phase at 175 °C, behavior characteristic of the Ge1Sb2Te4 composition. The average grain size is of about 100 nm after an annealing at 400 °C. The Ge14Sb49Te37 film crystallizes only in the hexagonal phase, with an average grain size of about 60 nm after annealing at 400 °C. The X-ray fluorescence analysis shows a non uniform distribution of the constituent atoms and in particular a Ge signal decrement and a Sb enrichment at grain boundaries. The in situ annealing of amorphous nano-areas (RESET state under a thermal stress) indicates a fast re-crystallization speed for Ge14Sb35Te51, 80 pm/s at 90 °C, and a lower speed for Ge14Sb49Te37, at 130 °C a grain growth velocity of 50 pm/s has been measured. The different behavior of the two alloys is discussed in terms of structural vacancies filling by the Sb atoms in excess and by their segregation at grain boundaries. The influence of the obtained results on the device characteristics is discussed.  相似文献   

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