The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity...The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease with the increase of the well width and decrease quickly when the well width is small. The binding energy of the ground state increases until it reaches a maximum value, and then decreases as the well width increases. The results are meaningful and can be widely applied in the design of various optoelectronie devices.展开更多
Nitrogen doping is applied to improve the thermal stability of SnTe.The crystallization temperature Tc of SnTe is below room temperature,which can be elevated to 216℃ by 7.65at.%nitrogen doping.Nitrogen doping result...Nitrogen doping is applied to improve the thermal stability of SnTe.The crystallization temperature Tc of SnTe is below room temperature,which can be elevated to 216℃ by 7.65at.%nitrogen doping.Nitrogen doping results in the formation of SnNx in the nitrogen doped SnTe(N-SnTe)materials,which hinders the movement of atoms and suppresses the crystallization,leading to a better thermal stability.The crystallization activation energy(Ea)and data retention for ten years of 7.65at.%N-SnTe are 1.89 eV and 81℃,respectively.Moreover,the voltage pulses have successfully triggered the SET and RESET operations of the N-SnTe based device at the voltage of 0.9 V and 2.6 V.The good thermal stability and reversible phase-change ability have proved the potential of N-SnTe for phase-change memory application.展开更多
The results of adhesion improvement and SET-RESET operation voltage reduction for the GeN buffer layer are presented.It is found that the adhesive strength between the Ge_(2)Sb_(2)Te_(5)(GST)layer and the layer below ...The results of adhesion improvement and SET-RESET operation voltage reduction for the GeN buffer layer are presented.It is found that the adhesive strength between the Ge_(2)Sb_(2)Te_(5)(GST)layer and the layer below could be increased at least 20 times,which is beneficial for solving the phase change material peeling issue in the fabrication process of phase change memory(PCM).Meanwhile,the RESET voltage of the PCM cell with a 3-nm-thick GeN buffer layer can be reduced from 3.5 V to 2.2 V.The GeN buffer layer will play an important role in high density and low power consumption PCM applications.展开更多
Hinged mirror arrays are widely utilized for display applications and optical communication.They can be fabricated by an self-assembly technique using the strain in lattice-mismatched epitaxial layers.A multilayer str...Hinged mirror arrays are widely utilized for display applications and optical communication.They can be fabricated by an self-assembly technique using the strain in lattice-mismatched epitaxial layers.A multilayer structure including a strain-compensated layer,a digital alloy sacrificial layer and a strain bilayer,is grown by molecular-beam epitaxy.Self-assembly hinged mirrors on a GaAs substrate have been successfully fabricated by photolithography and selective etching.The hinge fabrication method with a strain bilayer is simple and flexible.Structures formed by multiple hinged plates will enable the self-assembly of more complex three-dimensional microstructures.展开更多
Self-organized In_(0.5)Ga_(0.5) As/GaAs quantum island structure emitting at 1.35μm at room temperature has been successfully fabricated by molecular beam epitaxy via cycled(InAs)1/(GaAs)1 monolayer deposition method...Self-organized In_(0.5)Ga_(0.5) As/GaAs quantum island structure emitting at 1.35μm at room temperature has been successfully fabricated by molecular beam epitaxy via cycled(InAs)1/(GaAs)1 monolayer deposition method.Photoluminescence measurement shows that a very narrow linewidth of 19.2 meV at 300 K has been reached for the first time,indicating effective suppression of inhomogeneous broadening of optical emission from the In_(0.5)Ga_(0.5) As island structure due to indium segregation reduction by introducing an AlAs layer and the strain reduction by inserting an In0.2Ga0.8As layer overgrown on the top of islands.The mounds-like morphology of the islands elongated along the[1ī0]azimuth are observed by the atomic force microscopy measurement,which reveals the fact that strain in the islands is partially relaxed along the[1ī0]direction.Our results present important information for the fabrication of 1.3μm wavelength quantum dot devices.展开更多
Thermal induced interdiffusion in InAs/GaAs quantum dot superlattices is studied by high-resolution x-ray diffraction rocking curve and photoluminescence techniques.With increasing annealing temperature,up to 300 meV ...Thermal induced interdiffusion in InAs/GaAs quantum dot superlattices is studied by high-resolution x-ray diffraction rocking curve and photoluminescence techniques.With increasing annealing temperature,up to 300 meV a blueshift of the emission peak position and down to 16.6 meV a narrowing of the line width are found in photoluminescence spectra,and respective intensity of the higher-order satellite peaks to lower-order ones in the x-ray rocking curves decreases.Dynamical theory is employed to simulate the measured x-ray diffraction data.Excellent agreement between the experimental curves and the simulations is achieved when the composition,thickness and stress variations caused by interdiffusion are taken into account.It is found that the significant In-Ga intermixing occurs even in the as-grown InAs/GaAs quantum dots.The estimated diffusion coefficient is 1.8 × 10^(-17)cm^(2)·s^(-1) at 650℃,3.2 × 10^(-17)cm^(2)·s^(-1) at 750℃,and 1.2× 10^(-14)cm^(2)·s^(-1) at 850℃.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
An integrated phase change memory cell with dual trench epitaxial diode is successfully integrated in the traditional 0.13μm CMOS technology.By using dual trench isolated structure in the memory cell,it is feasible t...An integrated phase change memory cell with dual trench epitaxial diode is successfully integrated in the traditional 0.13μm CMOS technology.By using dual trench isolated structure in the memory cell,it is feasible to employ a Si-diode as a selector for integration in a crossbar structure for high-density phase change memory even at 45 nm technology node and beyond.A cross-point memory selector with a large on/off current ratio is demonstrated,the diode provides nine orders of magnitude isolation between forward and reverse biases in the SET state.A low SET programming current of 0.7mA is achieved and RESET/SET resistance difference of 10000×is obtained.展开更多
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (PRC)Foundation of Qufu Normal University under Grant No. XJ0622
文摘The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease with the increase of the well width and decrease quickly when the well width is small. The binding energy of the ground state increases until it reaches a maximum value, and then decreases as the well width increases. The results are meaningful and can be widely applied in the design of various optoelectronie devices.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB934300,2011CBA00607,2011CB9328004the National Integrate Circuit Research Program of China under Grant No 2009ZX02023-003+2 种基金the National Nat-ural Science Foundation of China under Grant Nos 60906004,60906003,61006087,61076121,61176122,61106001the Science and Technology Council of Shanghai under Grant Nos 11DZ2261000,1052nm07000,11QA1407800the Chinese Academy of Sciences under Grant No 20110490761.
文摘Nitrogen doping is applied to improve the thermal stability of SnTe.The crystallization temperature Tc of SnTe is below room temperature,which can be elevated to 216℃ by 7.65at.%nitrogen doping.Nitrogen doping results in the formation of SnNx in the nitrogen doped SnTe(N-SnTe)materials,which hinders the movement of atoms and suppresses the crystallization,leading to a better thermal stability.The crystallization activation energy(Ea)and data retention for ten years of 7.65at.%N-SnTe are 1.89 eV and 81℃,respectively.Moreover,the voltage pulses have successfully triggered the SET and RESET operations of the N-SnTe based device at the voltage of 0.9 V and 2.6 V.The good thermal stability and reversible phase-change ability have proved the potential of N-SnTe for phase-change memory application.
基金Supported by the National Basic Research Program of China(2010CB934300,2011CBA00607,2011CB932800)the National Integrate Circuit Research Program of China(2009ZX02023-003)+1 种基金the National Natural Science Foundation of China(60906004,60906003,61006087,61076121)the Science and Technology Council of Shanghai(1052nm07000).
文摘The results of adhesion improvement and SET-RESET operation voltage reduction for the GeN buffer layer are presented.It is found that the adhesive strength between the Ge_(2)Sb_(2)Te_(5)(GST)layer and the layer below could be increased at least 20 times,which is beneficial for solving the phase change material peeling issue in the fabrication process of phase change memory(PCM).Meanwhile,the RESET voltage of the PCM cell with a 3-nm-thick GeN buffer layer can be reduced from 3.5 V to 2.2 V.The GeN buffer layer will play an important role in high density and low power consumption PCM applications.
基金by the National Natural Science Foundation of China under Grant Nos 60976015 and 10990103the Natural Science Foundation of Shandong Province under Grant No ZR2010FM023the Open Project of State Key Laboratory of Functional Materials for Informatics.
文摘Hinged mirror arrays are widely utilized for display applications and optical communication.They can be fabricated by an self-assembly technique using the strain in lattice-mismatched epitaxial layers.A multilayer structure including a strain-compensated layer,a digital alloy sacrificial layer and a strain bilayer,is grown by molecular-beam epitaxy.Self-assembly hinged mirrors on a GaAs substrate have been successfully fabricated by photolithography and selective etching.The hinge fabrication method with a strain bilayer is simple and flexible.Structures formed by multiple hinged plates will enable the self-assembly of more complex three-dimensional microstructures.
基金Supported by the National Natural Science Foundation of China under Grant Nos.69876036 and 19823001Hundred Talent Program of Chinese Academy of Sciences,and State Climbing Research Project.
文摘Self-organized In_(0.5)Ga_(0.5) As/GaAs quantum island structure emitting at 1.35μm at room temperature has been successfully fabricated by molecular beam epitaxy via cycled(InAs)1/(GaAs)1 monolayer deposition method.Photoluminescence measurement shows that a very narrow linewidth of 19.2 meV at 300 K has been reached for the first time,indicating effective suppression of inhomogeneous broadening of optical emission from the In_(0.5)Ga_(0.5) As island structure due to indium segregation reduction by introducing an AlAs layer and the strain reduction by inserting an In0.2Ga0.8As layer overgrown on the top of islands.The mounds-like morphology of the islands elongated along the[1ī0]azimuth are observed by the atomic force microscopy measurement,which reveals the fact that strain in the islands is partially relaxed along the[1ī0]direction.Our results present important information for the fabrication of 1.3μm wavelength quantum dot devices.
基金Supported by the State Climbing Research project under Grant No.69776016.
文摘Thermal induced interdiffusion in InAs/GaAs quantum dot superlattices is studied by high-resolution x-ray diffraction rocking curve and photoluminescence techniques.With increasing annealing temperature,up to 300 meV a blueshift of the emission peak position and down to 16.6 meV a narrowing of the line width are found in photoluminescence spectra,and respective intensity of the higher-order satellite peaks to lower-order ones in the x-ray rocking curves decreases.Dynamical theory is employed to simulate the measured x-ray diffraction data.Excellent agreement between the experimental curves and the simulations is achieved when the composition,thickness and stress variations caused by interdiffusion are taken into account.It is found that the significant In-Ga intermixing occurs even in the as-grown InAs/GaAs quantum dots.The estimated diffusion coefficient is 1.8 × 10^(-17)cm^(2)·s^(-1) at 650℃,3.2 × 10^(-17)cm^(2)·s^(-1) at 750℃,and 1.2× 10^(-14)cm^(2)·s^(-1) at 850℃.
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 by the National Basic Research Program of China(2010CB934300,2011CB309602,2011CB932800)the National Integrated Circuit Research Program of China(2009ZX02023-003)+1 种基金the National Natural Science Foundation of China(60906004,60906003,61076121,61006087)the Science and Technology Council of Shanghai(1052nm07000).
文摘An integrated phase change memory cell with dual trench epitaxial diode is successfully integrated in the traditional 0.13μm CMOS technology.By using dual trench isolated structure in the memory cell,it is feasible to employ a Si-diode as a selector for integration in a crossbar structure for high-density phase change memory even at 45 nm technology node and beyond.A cross-point memory selector with a large on/off current ratio is demonstrated,the diode provides nine orders of magnitude isolation between forward and reverse biases in the SET state.A low SET programming current of 0.7mA is achieved and RESET/SET resistance difference of 10000×is obtained.
