An array of high power InGaN/GaN multi-quantum-well laser diodes with a broad waveguide is fabricated.The laser diode structure is grown on a GaN substrate by metal-organic chemical vapor deposition.The laser diode ar...An array of high power InGaN/GaN multi-quantum-well laser diodes with a broad waveguide is fabricated.The laser diode structure is grown on a GaN substrate by metal-organic chemical vapor deposition.The laser diode array consists of five emitter stripes which share common electrodes on one laser chip.The electrical and optical characteristics of the laser diode array are investigated under the pulse current injection with 10 kHz frequency and 100 ns pulse width.The laser diode array emits at the wavelength of 409 nm,which is located in the blue-violet region,and the threshold current is 2.9 A.The maximum output light peak power is measured to be 7.5 W at the wavelength of 411.8 nm under the current of 25 A.展开更多
An InGaN/GaN p-i-n solar cell inserted with a 5-nm low-temperature(LT)GaN interlayer between the p-GaN cap layer and the InGaN i-layer is grown on a c-plane sapphire substrate by metal organic chemical vapor depositio...An InGaN/GaN p-i-n solar cell inserted with a 5-nm low-temperature(LT)GaN interlayer between the p-GaN cap layer and the InGaN i-layer is grown on a c-plane sapphire substrate by metal organic chemical vapor deposition.The effects of the LT GaN interlayer on the performance of the InGaN/GaN solar cells are investigated.It is found that the LT-GaN interlayer prevents the extension of threading dislocations from the InGaN layer to the p-GaN layer and improves the crystal quality of both the p-GaN cap layer and the InGaN i-layer,ultimately leading to an increasing external quantum efficiency and photocurrent density of the InGaN/GaN solar cells.展开更多
We report the coherent resonant emission of the exciton state in a single InAs quantum dot,embedded in a planar optical microcavity.The quantum dot is excited by a laser beam from the cleaved sample edge,and the reson...We report the coherent resonant emission of the exciton state in a single InAs quantum dot,embedded in a planar optical microcavity.The quantum dot is excited by a laser beam from the cleaved sample edge,and the resonant fluorescence is collected in the direction perpendicular to the excitation laser beam,so the residual laser scattering can be deeply suppressed.This experimental setup enables us to observe Rabi oscillation and a Mollow triplet with Rabi energy up to about 27μeV.展开更多
We report on the formation of Ohmic contacts with low resistance and high thermal stability to N-face n-GaN for vertical structure light emitters using a Ti(50nm)/Pt(50nm)/Au(50nm)metal scheme,where the Pt layer is in...We report on the formation of Ohmic contacts with low resistance and high thermal stability to N-face n-GaN for vertical structure light emitters using a Ti(50nm)/Pt(50nm)/Au(50nm)metal scheme,where the Pt layer is introduced as a blocking layer to suppress the diffusion of Au onto the N-face n-GaN surface.It is shown that unlike the conventional Ti/A1/Ti/Au contacts,the Ti/Pt/Au contacts exhibit an Ohmic behavior with a relatively low specific contact resistivity of 1.1×10^(-4)Ω.cm^(2) even after annealing at 350℃.X-ray diffraction(XRD)measurements by synchrotron radiation and Auger electron spectroscopy(AES)examination are performed to understand the effects of heat treatment.展开更多
The photoluminescence (PL) of CdSe_(x)S_(1-x) semiconductor quantum dots (QDs) in a glass spherical microcavity is investigated. The CdSe_(x)S_(1-x) semiconductor clusters embedded in a glass matrix are fabricated by ...The photoluminescence (PL) of CdSe_(x)S_(1-x) semiconductor quantum dots (QDs) in a glass spherical microcavity is investigated. The CdSe_(x)S_(1-x) semiconductor clusters embedded in a glass matrix are fabricated by using the heat treatment method. Periodical structures consisting of sharp spectral lines are observed in the PL spectra of CdSe_(x)S_(1-x)QDs, which can be well explained by the coupling with the whispering gallery modes of the spherical microcavity based on Mie scattering theory.展开更多
The excitation transfer processes in vertically self-organized pairs of unequal-sized quantum dots(QD's),which are created in InAs/GaAs bilayers with different InAs deposition amounts in the first and second layer...The excitation transfer processes in vertically self-organized pairs of unequal-sized quantum dots(QD's),which are created in InAs/GaAs bilayers with different InAs deposition amounts in the first and second layers,have been investigated experimentally by photoluminescence technique.The distance between the two dot layers is varied from 3 to 12nm.The optical properties of the formed pairs of unequal-sized QD's with clearly discernible ground-state transition energy depend on the spacer thickness.When the spacer layer of GaAs is thin enough,only one photoluminescence peak related to the large QD ensemble has been observed as a result of strong electronic coupling in the InAs QD pairs.The results provide evidence for nonresonant energy transfer from the smaller QDs in the second layer to the larger QD's in the first layer in such an asymmetric QD pair.展开更多
The behavior of room temperature self-sustained current oscillations resulting from sequential resonance tunneling in a doped weakly-coupled GaAs/AlAs superlattice(SL)is investigated under hydrostatic pressure.From at...The behavior of room temperature self-sustained current oscillations resulting from sequential resonance tunneling in a doped weakly-coupled GaAs/AlAs superlattice(SL)is investigated under hydrostatic pressure.From atmosphere pressure to 6.5 kbar,oscillations exist in the whole plateau of the I-V curve and oscillating characteristics are affected by the pressure.When hydrostatic pressure is higher than 6.5 kbar,the current oscillations are completely suppressed although a current plateau still can be seen in the 1-V curve.The plateau disappears when the pressure is close to 13.5kbar.As the main effect of hydrostatic pressure is to lower the X point valley with respect to Г point valley,the disappearance of oscillation and the plateau shrinkage before Г-X resonance takes place are attributed to the increases of thermoionic emission and nonresonant tunneling components determined by the lowest Г-X barrier height in GaAs/AlAs SL structure.展开更多
基金Supported by the National Natural Science Foundation of China for Distinguished Young Scholars under Grant No 60925017the National Natural Science Foundation of China under Grant Nos 61223005,10990100,60836003 and 61176126Tsinghua National Laboratory for Information Science and Technology(TNList)Cross-Discipline Foundation.
文摘An array of high power InGaN/GaN multi-quantum-well laser diodes with a broad waveguide is fabricated.The laser diode structure is grown on a GaN substrate by metal-organic chemical vapor deposition.The laser diode array consists of five emitter stripes which share common electrodes on one laser chip.The electrical and optical characteristics of the laser diode array are investigated under the pulse current injection with 10 kHz frequency and 100 ns pulse width.The laser diode array emits at the wavelength of 409 nm,which is located in the blue-violet region,and the threshold current is 2.9 A.The maximum output light peak power is measured to be 7.5 W at the wavelength of 411.8 nm under the current of 25 A.
基金Supported by the National Science Fund for Distinguished Young Scholars(No 60925017)the National Natural Science Foundation of China(Nos 10990100,60836003 and 60976045)Tsinghua National Laboratory for Information Science and Technology(TNList)Cross-Discipline Foundation.
文摘An InGaN/GaN p-i-n solar cell inserted with a 5-nm low-temperature(LT)GaN interlayer between the p-GaN cap layer and the InGaN i-layer is grown on a c-plane sapphire substrate by metal organic chemical vapor deposition.The effects of the LT GaN interlayer on the performance of the InGaN/GaN solar cells are investigated.It is found that the LT-GaN interlayer prevents the extension of threading dislocations from the InGaN layer to the p-GaN layer and improves the crystal quality of both the p-GaN cap layer and the InGaN i-layer,ultimately leading to an increasing external quantum efficiency and photocurrent density of the InGaN/GaN solar cells.
基金Supported by the National Natural Science Foundation of China under Grant Nos 90921015,11074246.
文摘We report the coherent resonant emission of the exciton state in a single InAs quantum dot,embedded in a planar optical microcavity.The quantum dot is excited by a laser beam from the cleaved sample edge,and the resonant fluorescence is collected in the direction perpendicular to the excitation laser beam,so the residual laser scattering can be deeply suppressed.This experimental setup enables us to observe Rabi oscillation and a Mollow triplet with Rabi energy up to about 27μeV.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60506001,60976045,60836003,60776047 and 61076119the National Basic Research Program(2007CB936700)the National Science Foundation for Distinguished Young Scholar under Grant No 60925017.
文摘We report on the formation of Ohmic contacts with low resistance and high thermal stability to N-face n-GaN for vertical structure light emitters using a Ti(50nm)/Pt(50nm)/Au(50nm)metal scheme,where the Pt layer is introduced as a blocking layer to suppress the diffusion of Au onto the N-face n-GaN surface.It is shown that unlike the conventional Ti/A1/Ti/Au contacts,the Ti/Pt/Au contacts exhibit an Ohmic behavior with a relatively low specific contact resistivity of 1.1×10^(-4)Ω.cm^(2) even after annealing at 350℃.X-ray diffraction(XRD)measurements by synchrotron radiation and Auger electron spectroscopy(AES)examination are performed to understand the effects of heat treatment.
基金Supported by the National Natural Science Foundation of China under Grant Nos.29890217 and 69876037。
文摘The photoluminescence (PL) of CdSe_(x)S_(1-x) semiconductor quantum dots (QDs) in a glass spherical microcavity is investigated. The CdSe_(x)S_(1-x) semiconductor clusters embedded in a glass matrix are fabricated by using the heat treatment method. Periodical structures consisting of sharp spectral lines are observed in the PL spectra of CdSe_(x)S_(1-x)QDs, which can be well explained by the coupling with the whispering gallery modes of the spherical microcavity based on Mie scattering theory.
基金Supported by the National Natural Science Foundation of China under Grant Nos.69776016 and 19823001,and the State Key Program for Basic Research.
文摘The excitation transfer processes in vertically self-organized pairs of unequal-sized quantum dots(QD's),which are created in InAs/GaAs bilayers with different InAs deposition amounts in the first and second layers,have been investigated experimentally by photoluminescence technique.The distance between the two dot layers is varied from 3 to 12nm.The optical properties of the formed pairs of unequal-sized QD's with clearly discernible ground-state transition energy depend on the spacer thickness.When the spacer layer of GaAs is thin enough,only one photoluminescence peak related to the large QD ensemble has been observed as a result of strong electronic coupling in the InAs QD pairs.The results provide evidence for nonresonant energy transfer from the smaller QDs in the second layer to the larger QD's in the first layer in such an asymmetric QD pair.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19574071.
文摘The behavior of room temperature self-sustained current oscillations resulting from sequential resonance tunneling in a doped weakly-coupled GaAs/AlAs superlattice(SL)is investigated under hydrostatic pressure.From atmosphere pressure to 6.5 kbar,oscillations exist in the whole plateau of the I-V curve and oscillating characteristics are affected by the pressure.When hydrostatic pressure is higher than 6.5 kbar,the current oscillations are completely suppressed although a current plateau still can be seen in the 1-V curve.The plateau disappears when the pressure is close to 13.5kbar.As the main effect of hydrostatic pressure is to lower the X point valley with respect to Г point valley,the disappearance of oscillation and the plateau shrinkage before Г-X resonance takes place are attributed to the increases of thermoionic emission and nonresonant tunneling components determined by the lowest Г-X barrier height in GaAs/AlAs SL structure.
