We report on an improvement in the crystal quality of GaN film with an Ino.17Alo.83N interlayer grown by pulsed metal-organic chemical vapor deposition, which is in-plane lattice-matched to GaN films. The indium compo...We report on an improvement in the crystal quality of GaN film with an Ino.17Alo.83N interlayer grown by pulsed metal-organic chemical vapor deposition, which is in-plane lattice-matched to GaN films. The indium composition of about 17% and the reductions of both screw and edge threading dislocations （TDs） in GaN film with the InA1N interlayer are estimated by high resolution X-ray diffraction. Transmission electron microscopy （TEM） measurements are employed to understand the mechanism of reduction in TD density. Raman and photoluminescence measurements indicate that the InA1N interlayer can improve the crystal quality of GaN film, and verify that there is no additional residual stress induced into the GaN film with InA1N interlayer. Atomic force microscopy measurement shows that the InA1N interlayer brings in a smooth surface morphology of GaN film. All the results show that the insertion of the InA1N interlayer is a convenient method to achieve excellent crystal quality in GaN epitaxy.展开更多
The first finding of natural GaN crystals is reported in sediments from the East Pacific. They are identified by multiple micro-beam techniques such as TEM, EDS and EELS. Detailed examinations show that these GaN crys...The first finding of natural GaN crystals is reported in sediments from the East Pacific. They are identified by multiple micro-beam techniques such as TEM, EDS and EELS. Detailed examinations show that these GaN crystals are euhedral and authigenic, and belong to the hexagonal system (space group P63mc) with cell parameters: a = b = 0.3186 nm, c = 0.5178 nm. Structure data fit closely with those of the synthetic GaN crystals obtained from high-temperature and high-pressure experi- ments. Moreover, the nearly perfect euhedral form of the sample excludes the possible synthetic origin of the GaN crystals as artifacts with long transport. The sampling localities are located between the Clarion and Clipperton Fracture Zone in the East Pacific where ongoing hydrothermal activities, deformation, and volcanic eruptions are very intensive. It is sug- gested that the natural GaN crystals may form at relatively high-temperature and high-pressure condi- tions in geologic environments that have been af- fected by intense hydrothermal activities.展开更多
First-principles calculations on neutral metal impurities (Mg, Zn and Ca) in zinc blende GaN were studied. Formation energies were calculated for substitution on the gallium site, the nitrogen site and incorporation i...First-principles calculations on neutral metal impurities (Mg, Zn and Ca) in zinc blende GaN were studied. Formation energies were calculated for substitution on the gallium site, the nitrogen site and incorporation in the octahedral interstitial site and the tetrahedral interstitial sites. The calculated results show that the major defects studied have a high formation energy in excess of 5 eV, and the gallium substitutional site is favorable for incorporation. MgGa has particularly low formation energy 1.19 eV and can be expected to incorporate readily into GaN. The local crystal structural changes around the impurity in the lattice were studied after metal atoms occupying the gallium substitutional site. It shows that the lattice constant becomes bigger and the tetrahedral angle between impurities and its nearest N atom becomes smaller mainly due to the extended M-N bond length and big size of impurities atoms, which results in a local lattice distortion. The Zn-N (2.04 A) bond strength is the smallest among the three impurities which raises the formation energy. CaGa is unfavorable due to a large size mismatch in spite of a large bond strength (2.25 A). The calculated results identify the two key factors determining impurities incorporation in zinc blende GaN: the atomic size of impurities comparing to that of host atoms and the bond strength between the impurities and its neighbors. The results are in well agreement with other calculated and experimental results.展开更多
Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integra...Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integrated circuits.When used a s the material for LEDs and LDs,GaN has high transforming efficiencies and its d evice s have a long using lifetime of up to 10000 hours,several decuple times longer t han that of conventional light emitting diodes.As a semiconductor material for b lue/green light sources,GaN is non replaceable.It will have important applications in li g ht emitting devices,optical communication systems,compact disk(CD)players,full c olor copying devices,full color printers,high distinguishing laser printers,gr ea t screen full color displaying devices,and super thin TV displaying devices etc . In recent years,GaN has been the focus and hotspot of semiconductor industries,a nd its devices have a shining place in light emitting and laser industries. We synthesized GaN nanowires by a chemical vapor deposition (CVD)method.The nano wires have diameters from 20 nm to 60 nm,and the maximum length is up to 100 μ m .Following figure is the scanning electron microscopy (SEM)image of the as synt hesized GaN nanowires.展开更多
Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated cir...Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61076079,61274092,and 61204006)the Key Program of the National Natural Science Foundation of China(Grant No.61334002)
文摘We report on an improvement in the crystal quality of GaN film with an Ino.17Alo.83N interlayer grown by pulsed metal-organic chemical vapor deposition, which is in-plane lattice-matched to GaN films. The indium composition of about 17% and the reductions of both screw and edge threading dislocations （TDs） in GaN film with the InA1N interlayer are estimated by high resolution X-ray diffraction. Transmission electron microscopy （TEM） measurements are employed to understand the mechanism of reduction in TD density. Raman and photoluminescence measurements indicate that the InA1N interlayer can improve the crystal quality of GaN film, and verify that there is no additional residual stress induced into the GaN film with InA1N interlayer. Atomic force microscopy measurement shows that the InA1N interlayer brings in a smooth surface morphology of GaN film. All the results show that the insertion of the InA1N interlayer is a convenient method to achieve excellent crystal quality in GaN epitaxy.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 40372024 ＆ 49776295） as well as the China 0cean Mineral Resources R＆D Association （Grant Nos. DY105-01-03-02, DY105-01-04-02）.
文摘The first finding of natural GaN crystals is reported in sediments from the East Pacific. They are identified by multiple micro-beam techniques such as TEM, EDS and EELS. Detailed examinations show that these GaN crystals are euhedral and authigenic, and belong to the hexagonal system (space group P63mc) with cell parameters: a = b = 0.3186 nm, c = 0.5178 nm. Structure data fit closely with those of the synthetic GaN crystals obtained from high-temperature and high-pressure experi- ments. Moreover, the nearly perfect euhedral form of the sample excludes the possible synthetic origin of the GaN crystals as artifacts with long transport. The sampling localities are located between the Clarion and Clipperton Fracture Zone in the East Pacific where ongoing hydrothermal activities, deformation, and volcanic eruptions are very intensive. It is sug- gested that the natural GaN crystals may form at relatively high-temperature and high-pressure condi- tions in geologic environments that have been af- fected by intense hydrothermal activities.
基金Porject supported by National High-Tech Research and Development Program of China
文摘First-principles calculations on neutral metal impurities (Mg, Zn and Ca) in zinc blende GaN were studied. Formation energies were calculated for substitution on the gallium site, the nitrogen site and incorporation in the octahedral interstitial site and the tetrahedral interstitial sites. The calculated results show that the major defects studied have a high formation energy in excess of 5 eV, and the gallium substitutional site is favorable for incorporation. MgGa has particularly low formation energy 1.19 eV and can be expected to incorporate readily into GaN. The local crystal structural changes around the impurity in the lattice were studied after metal atoms occupying the gallium substitutional site. It shows that the lattice constant becomes bigger and the tetrahedral angle between impurities and its nearest N atom becomes smaller mainly due to the extended M-N bond length and big size of impurities atoms, which results in a local lattice distortion. The Zn-N (2.04 A) bond strength is the smallest among the three impurities which raises the formation energy. CaGa is unfavorable due to a large size mismatch in spite of a large bond strength (2.25 A). The calculated results identify the two key factors determining impurities incorporation in zinc blende GaN: the atomic size of impurities comparing to that of host atoms and the bond strength between the impurities and its neighbors. The results are in well agreement with other calculated and experimental results.
文摘Wurtzite structure gallium nitride, GaN,a direct bandgap semiconductor(3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ting diodes(LED),laser diodes(LD),and high power integrated circuits.When used a s the material for LEDs and LDs,GaN has high transforming efficiencies and its d evice s have a long using lifetime of up to 10000 hours,several decuple times longer t han that of conventional light emitting diodes.As a semiconductor material for b lue/green light sources,GaN is non replaceable.It will have important applications in li g ht emitting devices,optical communication systems,compact disk(CD)players,full c olor copying devices,full color printers,high distinguishing laser printers,gr ea t screen full color displaying devices,and super thin TV displaying devices etc . In recent years,GaN has been the focus and hotspot of semiconductor industries,a nd its devices have a shining place in light emitting and laser industries. We synthesized GaN nanowires by a chemical vapor deposition (CVD)method.The nano wires have diameters from 20 nm to 60 nm,and the maximum length is up to 100 μ m .Following figure is the scanning electron microscopy (SEM)image of the as synt hesized GaN nanowires.
文摘Wurtzite strcture gallium nitride, GaN,a direct bandgap semiconductor (3.4 eV at room temperature),is an ideal material for fabrication of blue/green light emit ti ng diodes, laser diodes,and high power integrated circuits.Recent progress in th in film crystal technique has realized the output of blue semiconductor lasers w i th a lifetime of over 10000 hours under continuous wave operation at room tempe r ature.So far GaN and its ternary indium and aluminum alloys are grown almost uni v ersally on foreign substrates with varying lattice mismatches.The mismatch undou btedly results in a significant dislocation density in the grown films.Hence it is necessary to grow single crystal GaN to be used as substrates for improvement of laser diodes.On the other hand,low dimensional GaN materials such as nanocry stalline powder,nanocrystal assembled bulk(nanophase) and nano wires are very u seful in both fundamental mesoscopic research and future development of GaN nano devices.Here we report our main recent progresses on the crystal growth of GaN a nd the preparation of its low dimensional materials.
