Strain accommodation of 3C-SiC grown on hydrogen-implanted Si (001) substrate

The hydrogen-implanted Si substrate has been used for the fabrication of the "compliant substrate", which can accommodate the mismatch strain during the heteroepitaxy. The compliance of the substrate can be modulated by the energy and dose of implanted hydrogen. In addition, the defects caused by implantation act as the gettering center for the internal gettering of the harmful metallic impurities. Compared with SiC films growth on substrate without implantation. all the measurements indicated that the mismatch strains in the SiC films grown on this substrate have been released and the crystalline qualities have been improved. It is a practical technique used for the compliant substrate fabrication and compatible with the semiconductor industry. (C) 2003 Elsevier B.V. All rights reserved.

Boron diffusion in Ge+ premorphized and BF2+ implanted Si(001)

The annealing behavior of Si implanted with Ge and then BF2 has been characterized by double crystal X-ray diffraction (DCXRD) and secondary ion mass spectroscopy (SIMS). The results show that annealing at 600 degrees C for 60 minutes can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. The initial crystallinity of Si is fully recovered after annealing at 950 degrees C for 60 minutes and accompanied by Ge diffusion. Very shallow boron junction depth has been formed. When annealing temperature rises to 1050 degrees C, B diffusion enhances, which leads to a deep diffusion and good distribution of B atoms into the Si substrate. The X-ray diffraction (004) rocking curves from the samples annealed at 1050 degrees C for 60 minutes display two SiGe peaks, which may be related to the B concentration profiles.

Boron diffusion in Ge+ premorphized and BF2+ implanted Si(001)

The annealing behavior of Si implanted with Ge and then BF2 has been characterized by double crystal X-ray diffraction (DCXRD) and secondary ion mass spectroscopy (SIMS). The results show that annealing at 600 degrees C for 60 minutes can only remove a little damage induced by implantation and nearly no redistribution of Ge and B atoms has occurred during the annealing. The initial crystallinity of Si is fully recovered after annealing at 950 degrees C for 60 minutes and accompanied by Ge diffusion. Very shallow boron junction depth has been formed. When annealing temperature rises to 1050 degrees C, B diffusion enhances, which leads to a deep diffusion and good distribution of B atoms into the Si substrate. The X-ray diffraction (004) rocking curves from the samples annealed at 1050 degrees C for 60 minutes display two SiGe peaks, which may be related to the B concentration profiles.

Cracking in hydrogen ion-implanted Si/Si0.8Ge0.2/Si heterostructures

We demonstrate that a controllable cracking can be realized in Si with a buried strain layer when hydrogen is introduced using traditional H-ion implantation techniques. However, H stimulated cracking is dependent on H projected ranges; cracking occurs along a Si0.8Ge0.2 strain layer only if the H projected range is shallower than the depth of the strained layer. The absence of cracking for H ranges deeper than the strain layer is attributed to ion-irradiation induced strain relaxation, which is confirmed by Rutherford-backscattering-spectrometry channeling angular scans. The study reveals the importance of strain in initializing continuous cracking with extremely low H concentrations.

Nanohardness and contact angle of Si wafers implanted with N and C and Al alloy with N by plasma ion implantation

Surfaces of silicon wafers implanted with N and C, respectively, and aluminum 5052 implanted with N alone by plasma immersion ion implantation WHO were probed by a nanoindentor and analyzed by the contact-angle method to provide information on surface nanohardness and wettability. Silicon nitride and silicon carbide are important ceramic materials for microelectronics, especially for high-temperature applications. These compounds can be synthesized by high-dose ion implantation. The nanohardness of a silicon sample implanted with 12-keV nitrogen PIII (with 3 X 10(17) cm(-2) dose) increased by 10% compared to the unimplanted sample, in layers deeper than the regions where the formation of the Si,N, compound occurred. A factor of 2.5 increase in hardness was obtained for C-implanted Si wafer at 35 keV (with 6 X 10(17) cm(-2) dose), again deeper than the SiC-rich layer, Both compounds are in the amorphous state and their hardness is much lower than that of the crystalline compounds, which require an annealing process after ion implantation. In the same targets, the contact angle increased by 65% and 35% for N- and C-implanted samples, respectively. Compared to the Si target, the nitrogen PIII-irradiated Al 5052 (wish 15 keV) showed negligible change in its hydrophobic character after ion implantation. Its near-surface nanohardness measurement showed a slight increase for doses of 1 X 10(17) cm(-2). We have been searching for an AlN layer of the order of 1000 A thick, using such a low-energy PIII process, but oxide formation during processing has precluded its synthesis. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Photoluminescence from Er-doped Si-in-SiNx thin films

Photoluminescence from Er3+-implanted Si-in-SiN, films emitting efficiently visible light were investigated. A Stark structure in the Er3+ photoluminescence spectrum was observed at room temperature, which reveals more than one site symmetry for the Er3+-centers in the Si-in-SiN, matrix. The correlation between the visible photoluminescence from the silicon nanoparticles and the 1.54 mu m emission from the Er3+-centers was discussed. (c) 2006 Elsevier B.V. All rights reserved.

Annealing and activation of silicon implanted in semi-insulating InP substrates

We have investigated the annealing and activation of silicon implanted in both as-grown Fe-doped semi-insulating (SI) InP substrate and undoped SI InP substrate obtained by annealing high purity conductive InP wafer (wafer-annealed). Si implantations were performed at an energy of 500 keV and a dose of 1 X 10(15) cm(-2). Following the implantations, rapid thermal annealing (RTA) cycles were carried out for 30 s at different temperatures. The results of Raman measurements show that for 700degreesC/30s RTA, the two Si-implanted SI InP substrates have acquired a high degree of lattice recovery and electrical activation. However, further Hall measurements indicate that the carrier concentration of the wafer-annealed SI InP substrate is about three times higher than that of the as-grown Fe-doped SI InP substrate. The difference can be ascribed to the low Fe concentration of the wafer-annealed SI InP substrate.These experimental data imply that the use of the wafer-annealed SI InP substrate can be conducive to the improvement of InP-based device performances. (C) 2003 Elsevier Ltd. All rights reserved.

Photoluminescence and activation on SI-GaAs by Si+ implantation and following rapid thermal annealing

Photoluminescence (PL) and electrical characteristics of SI-GaAs, Si+-implanted and following rapid thermal annealing (RTA), were investigated, The PL spectra of Si-GA-C-As, Ga-i-Si-As, and V-As-Si-As were obtained. This paper concentrates on the PL peak at 1.36 eV which was proven as an emission of the Si-Ga-V-Ga combination by Si+ + P+ dual implantation. The results indicate that the peak at 1.36 eV appears when the ratio of As:Ga increased during the processing. Also high activation was obtained for the sample under the same conditions. More discussion on the mechanism of Si+ implanted SI-GaAs has been made based on the Morrow model [J. Appl. Phys, 64 (1988) 1889].

Sub-bandgap spectral photo-response analysis of Ti supersaturated Si

We have analyzed the increase of the sheet conductance (ΔG□) under spectral illumination in high dose Ti implanted Si samples subsequently processed by pulsed-laser melting. Samples with Ti concentration clearly above the insulator-metal transition limit show a remarkably high ΔG□, even higher than that measured in a silicon reference sample. This increase in the ΔG□ magnitude is contrary to the classic understanding of recombination centers action and supports the lifetime recovery predicted for concentrations of deep levels above the insulator-metal transition.

Study of the Electrical Behavior in Intermediate Band-Si Junctions

In this study we analyze the electrical behavior of a junction formed by an ultraheavily Ti implanted Si layer processed by a Pulsed Laser Melting (PLM) and the non implanted Si substrate. This electrical behavior exhibits an electrical decoupling effect in this bilayer that we have associated to an Intermediate Band (IB) formation in the Ti supersaturated Si layer. Time-of-flight secondary ion mass spectrometry (ToFSIMS) measurements show a Ti depth profile with concentrations well above the theoretical limit required to the IB formation. Sheet resistance and Hall mobility measurements in the van der Pauw configuration of these bilayers exhibit a clear dependence with the different measurement currents introduced (1menor queA-1mA). We find that the electrical transport properties measured present an electrical decoupling effect in the bilayer as function of the temperature. The dependence of this effect with the injected current could be explained in terms of an additional current flow in the junction from the substrate to the IB layer and in terms of the voltage dependence in the junction with the measurement current.

Ruling out the impact of defects on the below band gap photoconductivity of Ti supersaturated Si

In this study, we present a structural and optoelectronic characterization of high dose Ti implanted Si subsequently pulsed-laser melted (Ti supersaturated Si). Time-of-flight secondary ion mass spectrometry analysis reveals that the theoretical Mott limit has been surpassed after the laser process and transmission electron microscopy images show a good lattice reconstruction. Optical characterization shows strong sub-band gap absorption related to the high Ti concentration. Photoconductivity measurements show that Ti supersaturated Si presents spectral response orders of magnitude higher than unimplanted Si at energies below the band gap. We conclude that the observed below band gap photoconductivity cannot be attributed to structural defects produced by the fabrication processes and suggest that both absorption coefficient of the new material and lifetime of photoexcited carriers have been enhanced due to the presence of a high Ti concentration. This remarkable result proves that Ti supersaturated Si is a promising material for both infrared detectors and high efficiency photovoltaic devices.

X-ray-diffraction study of quasipseudomorphic ErSi1.7 layers formed by channeled ion-beam synthesis

ErSi1.7 layers with high crystalline quality (chi(min) of Er is 1.5%) have been formed by 90 keV Er ion implantation to a dose of 1.6X10(17)/cm(2) at 450 degrees C using channeled implantation. The perpendicular and parallel elastic strain e(perpendicular to)=-0.94%+/-0.02% and e(parallel to)=1.24%+/-0.08% of the heteroepitaxial erbium silicide layers have been measured with symmetric and asymmetric x-ray reflections using a double-crystal x-ray diffractometer. The deduced tetragonal distortion e(T(XRD))=e(parallel to)-e(perpendicular to)=2.18%+/-0.10%, which is consistent with the value e(T(RBS))2.14+/-0.17% deduced from the Rutherford backscattering and channeling measurements. The quasipseudomorphic growth of the epilayer and the stiffness along a and c axes of the epilayer deduced from the x-ray diffraction are discussed.

Preparation and characterization of erbium doped sol-gel silica glasses

Erbium-doped silica glasses were made by sol-gel process. Intensive photoluminescence (PL) spectra from the Er-doped silica glasses at room temperature were measured. A broadband peak at 1535 ma, corresponding to the I-4(13/2)-I-4(15/2) transition, its full width at half-maximum (FWHM) of 10 nm, and a shoulder at 1546 nm in the PL spectra were observed. At lower temperatures, main line of 1535 nm and another line of 1552 Mn instead of 1546 nm appear. So two types of luminescence centers must exist in the samples at different temperature. The intensity of main line does not decrease obviously with increasing temperature. By varying the Er ion concentration in the range of 0.2 wt% - 5wt%, the highest photoluminescence intensity was obtained at 0.2wt% erbium doped concentration. Luminescence intensity decreases with increasing erbium concentration. Cooperative upconversion was used to explain the concentration quenching of luminescence from silica glass with high erbium concentration. Extended X-ray absorption fine structure measurements were carried out. It was found that the majority of the erbium impurities in the glasses have a local structure of eight first neighbor oxygen atoms at a mean distance of 0.255 nm, which is consistent with the typical coordination structure of rare earth ion.

Investigation of Mn-Implanted n-Si by Low-Energy Ion Beam Deposition

Mn ions were implanted to n-type Si(0 0 1) single crystal by low-energy ion beam deposition technique with an energy of 1000 eV and a dose of 7.5 x 10^{17} cm^{-2}. The samples were held at room temperature and at 300degreesC during implantation. Auger electron spectroscopy depth profiles of samples indicate that the Mn ions reach deeper in the sample implanted at 300degreesC than in the sample implanted at room temperature. X-ray diffraction measurements show that the structure of the sample implanted at room temperature is amorphous while that of the sample implanted at 300degreesC is crystallized. There are no new phases found except silicon both in the two samples. Atomic force microscopy images of samples indicate that the sample implanted at 300degreesC has island-like humps that cover the sample surface while there is no such kind of characteristic in the sample implanted at room temperature. The magnetic properties of samples were investigated by alternating gradient magnetometer (AGM). The sample implanted at 300degreesC shows ferromagnetic behavior at room temperature.

Investigation of Mn-implanted n-Si by low-energy ion beam deposition

Mn ions were implanted to n-type Si(0 0 1) single crystal by low-energy ion beam deposition technique with an energy of 1000 eV and a dose of 7.5 x 10(17) cm(-2). The samples were held at room temperature and at 300degreesC during implantation. Auger electron spectroscopy depth profiles of samples indicate that the Mn ions reach deeper in the sample implanted at 300degreesC than in the sample implanted at room temperature. X-ray diffraction measurements show that the structure of the sample implanted at room temperature is amorphous while that of the sample implanted at 300degreesC is crystallized. There are no new phases found except silicon both in the two samples. Atomic force microscopy images of samples indicate that the sample implanted at 300degreesC has island-like humps that cover the sample surface while there is no such kind of characteristic in the sample implanted at room temperature. The magnetic properties of samples were investigated by alternating gradient magnetometer (AGM). The sample implanted at 300degreesC shows ferromagnetic behavior at room temperature. (C) 2004 Elsevier BN. All rights reserved.