We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the ...We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).展开更多
Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15Ω.mm is obtained. It is found that the s...Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15Ω.mm is obtained. It is found that the sidewall obliquity near the regrown interface induced by the plasma dry etching has great influence on the total contact resistance. The fabricated device with a 100-nm T-shaped gate demonstrates a maximum drain current density of 0.95 A/mm at Vgs = 1 V and a maximum peak extrinsic transcondutance Gm of 216mS/ram. Moreover, a current gain cut-off frequency fT of 115 GHz and a maximum oscillation frequency fmax of 127 GHz are achieved.展开更多
ZnO thin films were grown on GaAs （001） substrates by metal-organic chemical vapor deposition （MOCVD） at low temperatures ranging from 100 to 400℃. DEZn and 1-12 O were used as the zinc precursor and oxygen precu...ZnO thin films were grown on GaAs （001） substrates by metal-organic chemical vapor deposition （MOCVD） at low temperatures ranging from 100 to 400℃. DEZn and 1-12 O were used as the zinc precursor and oxygen precursor, respectively. The effects of the growth temperatures on the growth characteristics and optical properties of ZnO films were investigated. The X-ray diffraction measurement （XRD） results indicated that all the thin films were grown with highly c- axis orientation. The surface morphologies and crystal properties of the films were critically dependent on the growth temperatures. Although there was no evidence of epitaxial growth, the scanning electron microscopy （SEM） image of ZnO film grown at 400℃ revealed the presence of ZnO microcrystallines with closed packed hexagon structure. The photoluminescence spectrum at room temperature showed only bright band-edge （3. 33eV） emissions with little or no deep-level e- mission related to defects.展开更多
A versatile metal-organic chemical vapor deposition （MOCVD） system was designed and constructed. Copper films were deposited on silicon （100） substrates by chemical vapor deposition （CVD） using Cu（hfac）2 as a ...A versatile metal-organic chemical vapor deposition （MOCVD） system was designed and constructed. Copper films were deposited on silicon （100） substrates by chemical vapor deposition （CVD） using Cu（hfac）2 as a precursor. The growth of Cu nucleus on silicon substrates by H2 reduction of Cu（hfac）2 was studied by atomic force microscopy and scanning electron microscopy. The growth mode of Cu nucleus is initially Volmer-Weber mode （island）, and then transforms to Stranski-Rastanov mode （layer-by-layer plus island）. The mechanism of Cu nucleation on silicon （100） substrates was further investigated by X-ray photoelectron spectroscopy. From Cu2p, O1s, F1s, Si2p patterns, the observed C=O, OH and CF3/CF2 should belong to Cu（hfac） formed by the thermal dissociation of Cu（hfac）2. H2 reacts with hfac on the surface, producing OH. With its accumulation, OH reacts with hfac, forming HO-hfac, and desorbs, meanwhile, the copper oxide is reduced, and thus the redox reaction between Cu（hafc）2 and H2 occurs.展开更多
Metal-organic chemical vapor deposition （MOCVD） grown ferromagnetic GaMnN films are investigated by photo- luminescence （PL） measurement with a mid-gap excitation wavelength of 405 nm. A sharp PL peak at 1.8 eV is...Metal-organic chemical vapor deposition （MOCVD） grown ferromagnetic GaMnN films are investigated by photo- luminescence （PL） measurement with a mid-gap excitation wavelength of 405 nm. A sharp PL peak at 1.8 eV is found and the PL intensity successively decreases with the addition of Mn, in which the Mn concentration of sample A is below 1% （[Mn]A =0.75%） but its PL intensity is stronger than other samples＇. The 1.8-eV PL peak is attributed to the recombination of electrons in the t2 state of the neutral Mn3＋ acceptor with holes in the valence band. With Mn concentration increasing, the intensity of the PL peak decreases and the magnetic increment reduces in our samples. The correlation between the PL peak intensity and ferromagnetism of the samples is discussed in combination with the experimental results.展开更多
GaSb quantum dots have been widely applied in optoelectronic devices due to its unique electrical and optical properties.The effects of metal-organic chemical vapor deposition（MOCVD） parameters,such as growth temper...GaSb quantum dots have been widely applied in optoelectronic devices due to its unique electrical and optical properties.The effects of metal-organic chemical vapor deposition（MOCVD） parameters,such as growth temperature and vapour V/Ⅲ ratio[V/Ⅲ ratio means the molar ratio of trimethylgallium（TMGa） and triethylantimony（TESb）],were systematically investigated to achieve GaSb quantum dots with high quality and high density.The features of surface morphology of uncapped GaSb quantum dots were characterized by atomic force microscope（AFM） images.The results show that the surface morphologies of quantum dots are strongly dependent on growth temperature and vapour V/Ⅲ ratio.GaSb quantum dots with an average height of 4.94 nm and a density of 2.45× 1010 cm-2 were obtained by optimizing growth temperature and V/Ⅲ ratio.展开更多
ZnO thin films were grown on Si （111） substrates by low-pressure metal-organic chemical vapor deposition. The crystal structures and electrical properties of as-grown sample were investigated by scanning electron mi...ZnO thin films were grown on Si （111） substrates by low-pressure metal-organic chemical vapor deposition. The crystal structures and electrical properties of as-grown sample were investigated by scanning electron microscopy （SEM） and conductive atomic force microscopy （C-AFM）. It can be seen that with increasing growth temperature, the surface morphology of ZnO thin films changed from flake-like to cobblestones-like structure. The current maps were simultaneously recorded with the topography, which was gained by C-AFM contact mode. Conductivity for the off-axis facet planes presented on ZnO grains enhanced. Measurement results indicate that the off-axis facet planes were more electrically active than the c-plane of ZnO flakes or particles probably due to lower Schottky barrier height of the off-axis facet planes.展开更多
For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO th...For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition （MOCVD）. The properties of the ZnO films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and photoluminescence （PL） spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.展开更多
This paper studied the low-resistance ohmic contacts on InAlN/GaN with metal–organic chemical vapor deposition(MOCVD)regrowth technique.The 150-nm regrown n-InGaN exhibits a low sheet resistance of 31Ω/□,resulting ...This paper studied the low-resistance ohmic contacts on InAlN/GaN with metal–organic chemical vapor deposition(MOCVD)regrowth technique.The 150-nm regrown n-InGaN exhibits a low sheet resistance of 31Ω/□,resulting in an extremely low contact resistance of 0.102Ω·mm between n^(+)-InGaN and InAlN/GaN channels.Mask-free regrowth process was also used to significantly improve the sheet resistance of InAlN/GaN with MOCVD regrown ohmic contacts.Then,the diffusion mechanism between n^(+)-InGaN and InAlN during regrowth process was investigated with electrical and structural characterizations,which could benefit the further process optimization.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61974141)Tianjin Municipal Science and Technology BureauScience and Technology Innovation Bureau of China-Singapore Tianjin Eco-City。
文摘We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).
基金Supported by the National Natural Science Foundation of China under Grant No 61306113
文摘Nonalloyed ohmic contacts regrown by metal-organic chemical vapor deposition are performed on AlGaN/GaN high-electron-mobility transistors. Low ohmic contact resistance of 0.15Ω.mm is obtained. It is found that the sidewall obliquity near the regrown interface induced by the plasma dry etching has great influence on the total contact resistance. The fabricated device with a 100-nm T-shaped gate demonstrates a maximum drain current density of 0.95 A/mm at Vgs = 1 V and a maximum peak extrinsic transcondutance Gm of 216mS/ram. Moreover, a current gain cut-off frequency fT of 115 GHz and a maximum oscillation frequency fmax of 127 GHz are achieved.
文摘ZnO thin films were grown on GaAs （001） substrates by metal-organic chemical vapor deposition （MOCVD） at low temperatures ranging from 100 to 400℃. DEZn and 1-12 O were used as the zinc precursor and oxygen precursor, respectively. The effects of the growth temperatures on the growth characteristics and optical properties of ZnO films were investigated. The X-ray diffraction measurement （XRD） results indicated that all the thin films were grown with highly c- axis orientation. The surface morphologies and crystal properties of the films were critically dependent on the growth temperatures. Although there was no evidence of epitaxial growth, the scanning electron microscopy （SEM） image of ZnO film grown at 400℃ revealed the presence of ZnO microcrystallines with closed packed hexagon structure. The photoluminescence spectrum at room temperature showed only bright band-edge （3. 33eV） emissions with little or no deep-level e- mission related to defects.
基金ACKN0WLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20576112）.
文摘A versatile metal-organic chemical vapor deposition （MOCVD） system was designed and constructed. Copper films were deposited on silicon （100） substrates by chemical vapor deposition （CVD） using Cu（hfac）2 as a precursor. The growth of Cu nucleus on silicon substrates by H2 reduction of Cu（hfac）2 was studied by atomic force microscopy and scanning electron microscopy. The growth mode of Cu nucleus is initially Volmer-Weber mode （island）, and then transforms to Stranski-Rastanov mode （layer-by-layer plus island）. The mechanism of Cu nucleation on silicon （100） substrates was further investigated by X-ray photoelectron spectroscopy. From Cu2p, O1s, F1s, Si2p patterns, the observed C=O, OH and CF3/CF2 should belong to Cu（hfac） formed by the thermal dissociation of Cu（hfac）2. H2 reacts with hfac on the surface, producing OH. With its accumulation, OH reacts with hfac, forming HO-hfac, and desorbs, meanwhile, the copper oxide is reduced, and thus the redox reaction between Cu（hafc）2 and H2 occurs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61204008,11075176,and 60976090)the National Key Basic Research Special Foundation of China(Grant No.2013CB328705)
文摘Metal-organic chemical vapor deposition （MOCVD） grown ferromagnetic GaMnN films are investigated by photo- luminescence （PL） measurement with a mid-gap excitation wavelength of 405 nm. A sharp PL peak at 1.8 eV is found and the PL intensity successively decreases with the addition of Mn, in which the Mn concentration of sample A is below 1% （[Mn]A =0.75%） but its PL intensity is stronger than other samples＇. The 1.8-eV PL peak is attributed to the recombination of electrons in the t2 state of the neutral Mn3＋ acceptor with holes in the valence band. With Mn concentration increasing, the intensity of the PL peak decreases and the magnetic increment reduces in our samples. The correlation between the PL peak intensity and ferromagnetism of the samples is discussed in combination with the experimental results.
基金Supported by the National Natural Science Foundation of China（No.61076010） and the Program of the State Key Laboratory on Integrated Optoelectronics, China（No. IOSKL2012ZZ13）.
文摘GaSb quantum dots have been widely applied in optoelectronic devices due to its unique electrical and optical properties.The effects of metal-organic chemical vapor deposition（MOCVD） parameters,such as growth temperature and vapour V/Ⅲ ratio[V/Ⅲ ratio means the molar ratio of trimethylgallium（TMGa） and triethylantimony（TESb）],were systematically investigated to achieve GaSb quantum dots with high quality and high density.The features of surface morphology of uncapped GaSb quantum dots were characterized by atomic force microscope（AFM） images.The results show that the surface morphologies of quantum dots are strongly dependent on growth temperature and vapour V/Ⅲ ratio.GaSb quantum dots with an average height of 4.94 nm and a density of 2.45× 1010 cm-2 were obtained by optimizing growth temperature and V/Ⅲ ratio.
基金financially supported by the National Natural Science Foundation of China (Nos. 11175038 and 51102036)the Fundamental Research Funds for the Central Universities (No. DC110314)
文摘ZnO thin films were grown on Si （111） substrates by low-pressure metal-organic chemical vapor deposition. The crystal structures and electrical properties of as-grown sample were investigated by scanning electron microscopy （SEM） and conductive atomic force microscopy （C-AFM）. It can be seen that with increasing growth temperature, the surface morphology of ZnO thin films changed from flake-like to cobblestones-like structure. The current maps were simultaneously recorded with the topography, which was gained by C-AFM contact mode. Conductivity for the off-axis facet planes presented on ZnO grains enhanced. Measurement results indicate that the off-axis facet planes were more electrically active than the c-plane of ZnO flakes or particles probably due to lower Schottky barrier height of the off-axis facet planes.
文摘For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition （MOCVD）. The properties of the ZnO films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and photoluminescence （PL） spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.
基金the Fundamental Research Funds for the National Key Research and Development Project of China(Grant No.2020YFB1807403)the National Natural Science Foundation of China(Grant Nos.62174125 and 62131014)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.QTZX22022 and YJS2213)the Innovation Fund of Xidian University.
文摘This paper studied the low-resistance ohmic contacts on InAlN/GaN with metal–organic chemical vapor deposition(MOCVD)regrowth technique.The 150-nm regrown n-InGaN exhibits a low sheet resistance of 31Ω/□,resulting in an extremely low contact resistance of 0.102Ω·mm between n^(+)-InGaN and InAlN/GaN channels.Mask-free regrowth process was also used to significantly improve the sheet resistance of InAlN/GaN with MOCVD regrown ohmic contacts.Then,the diffusion mechanism between n^(+)-InGaN and InAlN during regrowth process was investigated with electrical and structural characterizations,which could benefit the further process optimization.
