An A1GaN/GaN superlattice grown on the top of a GaN buffer induces the broadening of the full width at half maximum of (102) and (002) X-ray diffraction rocking curves. With an increase in the Si-doped concentrati...An A1GaN/GaN superlattice grown on the top of a GaN buffer induces the broadening of the full width at half maximum of (102) and (002) X-ray diffraction rocking curves. With an increase in the Si-doped concentration in the GaN wells, the full width at half maximum of the (102) rocking curves decreases, while that of the (002) rocking curves increases. A significant increase of the full width at the half maximum of the (002) rocking curves when the doping concentration reaches 2.5 × 10^19 cm-3 indicates the substantial increase of the inclined threading dislocation. High level doping in the A1GaN/GaN superlattice can greatly reduce the biaxial stress and optimize the surface roughness of the structures grown on the top of it.展开更多
Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photol...Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) analyses shaw a strong dependence of the PL and XRD linewidths, XRD intensity ratio (Lepi/Isub), and lattice-mismatch on the substrate temperature. The X-ray diffraction peaks of samples grown at law temperatures show a composition of smaller peaks, indicating the presence of disorder due to alloy clustering. Raman scattering measurements of the same samples show an additional higher energy mode at 273 cm-1 in addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes. Samples doped with Si show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. Supported be observations of a reduction in both the AlAs-like and InAs-like LO phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also shows in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.展开更多
Influences of the Si doping on the structural and optical properties of the InGaN epilayers are investigated in detail by means of high-resolution X-ray diffraction (HRXRD), photolumimescence (PL), scanning electr...Influences of the Si doping on the structural and optical properties of the InGaN epilayers are investigated in detail by means of high-resolution X-ray diffraction (HRXRD), photolumimescence (PL), scanning electron microscope (SEM), and atomic force microscopy (AFM). It is found that the Si doping may improve the surface morphology and crystal quality of the InGaN film and meanwhile it can also enhance the emission efficiency by increasing the electron concentration in the InGaN and suppressing tile formation of V-defects, which act as nonradiative recombination centers in the InGaN, and it is proposed that the former plays a more important role in enhancing the emission efficiency in the InGaN.展开更多
In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons(ABPNRs) are mainly studied by using the non-equilibrium Green function method combined with the ...In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons(ABPNRs) are mainly studied by using the non-equilibrium Green function method combined with the spin-polarized density function theory. Our calculated electronic structures indicate that the edge hydrogenated ABPNRs exhibit a ferromagnetic bipolar magnetic semiconductor property, and that the Si atom doping can make ABPNRs convert into up-spin dominated half metal. The spin-resolved transport property results show that the doped devices can realize 100% spinfiltering function, and that the interesting negative differential resistance phenomenon can be observed. Our calculations suggest that the ABPNRs can be constructed as a spin heterojunction by introducing Si doping partially, and it would be used as a spin-diode for nano-spintronics in future.展开更多
The effects of Si doping on morphology, components and structure characteristics of CVD diamond films were studied. Si-doped CVD diamond films were deposited on Si substrate by adding tetraethoxysilane (TEOS) into a...The effects of Si doping on morphology, components and structure characteristics of CVD diamond films were studied. Si-doped CVD diamond films were deposited on Si substrate by adding tetraethoxysilane (TEOS) into acetone as source of reactant gas. The morphology and microstructure of diamond films were characterized by scanning electron microcopy (SEM). The crystalline quality of diamond films was studied by Raman spectroscopy and X-ray diffractometry (XRD). The surface roughness of the films was evaluated with surface profilometer. The results suggest that Si doping tends to reduce the crystallite size, enhance grain refinement and inhibit the appearance of (11 I) facets. Raman spectra indicate that Si doping can enhance the formation of sp2 phase in diamond films. Moreover, Raman signal of SiC was detected, which suggests the existence of Si in the diamond films. Smooth fine-grained diamond (SFGD) film was synthesized at Si to C ratio of 1%.展开更多
In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive index...In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive indexes ofβ-Ga_(2)O_(3) thin film are explained well with the new model,leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for theβ-Ga_(2)O_(3) thin film.Then,the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-dopedβ-Ga_(2)O_(3) thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion.Meanwhile,effective optical bandgap values of Si-dopedβ-Ga_(2)O_(3) thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly.In addition,the sub-bandgap absorption coefficients of Si-dopedβ-Ga_(2)O_(3) thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities.The theoretical absorption coefficients agree with the available experimental data.These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-dopedβ-Ga_(2)O_(3) thin films.展开更多
Due to ineffectiveness of routine IR-absorption method for determinahon of intershtial oxygen in heavily doped silicon, a 'peak-height' method has been dcveloped. The phosphorus-doped CZ-Si with n=(7.l~l2)...Due to ineffectiveness of routine IR-absorption method for determinahon of intershtial oxygen in heavily doped silicon, a 'peak-height' method has been dcveloped. The phosphorus-doped CZ-Si with n=(7.l~l2)× 10~17cm^(-3) was taken as sample for characterization. The calculation results at 300 K and 10 K were ptesented in detail. The'peak-height' method is much simpler than 'short-baseline' and 'curved-baseline' methods.展开更多
We report on the fabrication and characterization of InAs/GaAs chirped multilayer quantum-dot superluminescent diodes(CMQD-SLDs)with and without direct Si doping in QDs.It was found that both the output power and the ...We report on the fabrication and characterization of InAs/GaAs chirped multilayer quantum-dot superluminescent diodes(CMQD-SLDs)with and without direct Si doping in QDs.It was found that both the output power and the spectral width of the CMQD-SLDs were significantly enhanced by direct Si doping in the QDs.The output power and spectral width have been increased by approximately 18.3%and 40%,respectively.Moreover,we shortened the cavity length of the doped CMQD-SLD and obtained a spectral width of 106 nm.In addition,the maximum output power and spectral width of the CMQD-SLD doped directly with Si can be further increased to 16.6 mW and 114 nm,respectively,through anti-reflection coating and device packaging.The device exhibited the smallest spectral dip of 0.2 dB when the spectrum was widest.The improved performances of the doped CMQD-SLD can be attributed to the direct doping of Si in the QDs,optimization of device structure and device packaging.展开更多
基金Project supported by the National Key Science & Technology Special Project of China (Grant No. 2008ZX01002-002)the Major Program and State Key Program of National Natural Science Foundation of China (Grant No. 60890191)
文摘An A1GaN/GaN superlattice grown on the top of a GaN buffer induces the broadening of the full width at half maximum of (102) and (002) X-ray diffraction rocking curves. With an increase in the Si-doped concentration in the GaN wells, the full width at half maximum of the (102) rocking curves decreases, while that of the (002) rocking curves increases. A significant increase of the full width at the half maximum of the (002) rocking curves when the doping concentration reaches 2.5 × 10^19 cm-3 indicates the substantial increase of the inclined threading dislocation. High level doping in the A1GaN/GaN superlattice can greatly reduce the biaxial stress and optimize the surface roughness of the structures grown on the top of it.
文摘Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at a wide range of substrate tempreatures (470~550℃) and at different Si doping levels has been carried out. Low temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) analyses shaw a strong dependence of the PL and XRD linewidths, XRD intensity ratio (Lepi/Isub), and lattice-mismatch on the substrate temperature. The X-ray diffraction peaks of samples grown at law temperatures show a composition of smaller peaks, indicating the presence of disorder due to alloy clustering. Raman scattering measurements of the same samples show an additional higher energy mode at 273 cm-1 in addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes. Samples doped with Si show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. Supported be observations of a reduction in both the AlAs-like and InAs-like LO phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also shows in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.
基金Project supported by the National High Technology Research and Development Program of China (Grant Nos.2011AA03A112,2011AA03A106,and 2013AA03A101)the National Natural Science Foundation of China (Grant Nos.11204360,61210014,and 61078046)+2 种基金the Science & Technology Innovation Program of Department of Education of Guangdong Province,China (Grant No.2012CXZD0017)the Industry–Academia Research Union Special Fund of Guangdong Province,China (Grant No.2012B091000169)the Science & Technology Innovation Platform of Industry–Academia Research Union of Guangdong Province–Ministry Cooperation Special Fund,China (Grant No.2012B090600038)
文摘Influences of the Si doping on the structural and optical properties of the InGaN epilayers are investigated in detail by means of high-resolution X-ray diffraction (HRXRD), photolumimescence (PL), scanning electron microscope (SEM), and atomic force microscopy (AFM). It is found that the Si doping may improve the surface morphology and crystal quality of the InGaN film and meanwhile it can also enhance the emission efficiency by increasing the electron concentration in the InGaN and suppressing tile formation of V-defects, which act as nonradiative recombination centers in the InGaN, and it is proposed that the former plays a more important role in enhancing the emission efficiency in the InGaN.
基金Project supported by the National Natural Science Foundation of China(Grant No.21673296)the Hunan Provincial Natural Science Foundation of China(Grant No.2018JJ2481)the Fundamental Research Funds for the Central Universities of Central South University,China(Grant No.2018zzts328)
文摘In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons(ABPNRs) are mainly studied by using the non-equilibrium Green function method combined with the spin-polarized density function theory. Our calculated electronic structures indicate that the edge hydrogenated ABPNRs exhibit a ferromagnetic bipolar magnetic semiconductor property, and that the Si atom doping can make ABPNRs convert into up-spin dominated half metal. The spin-resolved transport property results show that the doped devices can realize 100% spinfiltering function, and that the interesting negative differential resistance phenomenon can be observed. Our calculations suggest that the ABPNRs can be constructed as a spin heterojunction by introducing Si doping partially, and it would be used as a spin-diode for nano-spintronics in future.
基金Project(51275302)supported by the National Natural Science Foundation of ChinaProject(BC2012124)supported by Technical Innovation Funds for the Sci-Tech Enterprise of Jiangsu Province,China
文摘The effects of Si doping on morphology, components and structure characteristics of CVD diamond films were studied. Si-doped CVD diamond films were deposited on Si substrate by adding tetraethoxysilane (TEOS) into acetone as source of reactant gas. The morphology and microstructure of diamond films were characterized by scanning electron microcopy (SEM). The crystalline quality of diamond films was studied by Raman spectroscopy and X-ray diffractometry (XRD). The surface roughness of the films was evaluated with surface profilometer. The results suggest that Si doping tends to reduce the crystallite size, enhance grain refinement and inhibit the appearance of (11 I) facets. Raman spectra indicate that Si doping can enhance the formation of sp2 phase in diamond films. Moreover, Raman signal of SiC was detected, which suggests the existence of Si in the diamond films. Smooth fine-grained diamond (SFGD) film was synthesized at Si to C ratio of 1%.
基金This study was financially supported by the National Natural Science Foundation of China(No.12074324)the Shenzhen Municipal Science and Technology Innovation Council(No.JCJY20180508163404043).
文摘In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive indexes ofβ-Ga_(2)O_(3) thin film are explained well with the new model,leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for theβ-Ga_(2)O_(3) thin film.Then,the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-dopedβ-Ga_(2)O_(3) thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion.Meanwhile,effective optical bandgap values of Si-dopedβ-Ga_(2)O_(3) thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly.In addition,the sub-bandgap absorption coefficients of Si-dopedβ-Ga_(2)O_(3) thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities.The theoretical absorption coefficients agree with the available experimental data.These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-dopedβ-Ga_(2)O_(3) thin films.
文摘Due to ineffectiveness of routine IR-absorption method for determinahon of intershtial oxygen in heavily doped silicon, a 'peak-height' method has been dcveloped. The phosphorus-doped CZ-Si with n=(7.l~l2)× 10~17cm^(-3) was taken as sample for characterization. The calculation results at 300 K and 10 K were ptesented in detail. The'peak-height' method is much simpler than 'short-baseline' and 'curved-baseline' methods.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.62035012,62074143,and 62004191)Zhejiang Lab (Grant No.2020LC0AD02)
文摘We report on the fabrication and characterization of InAs/GaAs chirped multilayer quantum-dot superluminescent diodes(CMQD-SLDs)with and without direct Si doping in QDs.It was found that both the output power and the spectral width of the CMQD-SLDs were significantly enhanced by direct Si doping in the QDs.The output power and spectral width have been increased by approximately 18.3%and 40%,respectively.Moreover,we shortened the cavity length of the doped CMQD-SLD and obtained a spectral width of 106 nm.In addition,the maximum output power and spectral width of the CMQD-SLD doped directly with Si can be further increased to 16.6 mW and 114 nm,respectively,through anti-reflection coating and device packaging.The device exhibited the smallest spectral dip of 0.2 dB when the spectrum was widest.The improved performances of the doped CMQD-SLD can be attributed to the direct doping of Si in the QDs,optimization of device structure and device packaging.