GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double ...GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double heterostructure which introduces an additional p-GaN insertion layer into traditional p-HFETs.The impact of the device structure on the hole densities and valence band energies of both the upper and lower channels is analyzed by using Silvaco TACD simulations,including the thickness of the upper AlGaN layer and the doping impurities and concentration in the GaN buffer layer,as well as the thickness and Mg-doping concentration in the p-GaN insertion layer.With the help of the p-GaN insertion layer,the C-doping concentration in the GaN buffer layer can be reduced,while the density of the two-dimensional hole gas in the lower channel is enhanced at the same time.This work suggests that a double heterostructure with a p-GaN insertion layer is a better approach to improve p-HFETs compared with those devices with C-doped buffer layer alone.展开更多
Layered two dimensional(2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites ca...Layered two dimensional(2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites can be obtained by cutting 3D perovskites along < 100 > orientation by incorporation of bulky organic spacers, which play a key role in the performance of 2D perovskite solar cells(PSCs). Compared with aliphatic spacers, aromatic spacers with high dielectric constant have the potential to decrease the dielectric and quantum confinement effect of 2D perovskites, promote efficient charge transport and reduce the exciton binding energy, all of which are beneficial for the photovoltaic performance of 2D PSCs. In this review, we aim to provide useful guidelines for the design of aromatic spacers for 2D perovskites. We systematically reviewed the recent progress of aromatic spacers used in 2D PSCs. Finally, we propose the possible design strategies for aromatic spacers that may lead to more efficient and stable 2D PSCs.展开更多
The influences of the spacer-layer Ta on the structures and magnetic properties of NdFeB/NdCeFeB multilayer films are investigated via DC sputtering under an Ar pressure of 1.2 Pa. An obvious （00l） texture of the ha...The influences of the spacer-layer Ta on the structures and magnetic properties of NdFeB/NdCeFeB multilayer films are investigated via DC sputtering under an Ar pressure of 1.2 Pa. An obvious （00l） texture of the hard phase is observed in each of the films, which indicates that the main phase of the film does not significantly change with Ta spacer-layer thickness. As a result, both the remanence and the saturation magnetization of the magnet first increase and then decrease, and the maximum values of 4π Mr and Hcj are 10.4 kGs （1 Gs=10^-4 T） and 15.0 kOe （1 Oe=79.5775 A·m^-1） for the film with a 2-nm-thick Ta spacer-layer, respectively, where the crystalline structures are columnar shape particles. The measured relationship between irreversible portion D （H）=-△ Mirr/2Mr and H indicates that the nucleation field of the film decreases with spacer layer thickness increasing, owing to slightly disordered grains near the interface between different magnetic layers.展开更多
We theoretically study the influence of spacer layer thickness fluctuation（SLTF） on the mobility of a twodimensional electron gas（2DEG） in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The d...We theoretically study the influence of spacer layer thickness fluctuation（SLTF） on the mobility of a twodimensional electron gas（2DEG） in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer.展开更多
An electron transporting material of TFTTP （4-（5-hexylthiophene-2-yl）-2,6-bis（5-trifluoromethyl）thiophen-2-yl）pyridine） was investigated as a cathode buffer layer to enhance the power efficiency of organic sola...An electron transporting material of TFTTP （4-（5-hexylthiophene-2-yl）-2,6-bis（5-trifluoromethyl）thiophen-2-yl）pyridine） was investigated as a cathode buffer layer to enhance the power efficiency of organic solar cells （OSCs） based on subphthalocyanine and C60. The overall power conversion efficiency was increased by a factor of 1.31 by inserting the TFTTP interfacial layer between the active layer and metallic cathode. The inner mechanism responsible for the performance enhancement of OSCs was systematically studied with the simulation of dark diode behavior and optical field distribution inside the devices as well as the characterization of device photocurrent. The results showed that the TFTTP layer could significantly increase the built-in potential in the devices, leading to the enhanced dissociation of charge transfer excitons. In addition, by using TFTTP as the buffer layer, a better Ohmic contact at C60/metal interface was formed, facilitating more efficient free charge carrier collection.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62104184,62234009,62090014,62188102,62104178,and 62104179)the Fundamental Research Funds for the Central Universities of China(Grant Nos.YJSJ23019,XJSJ23047,and ZDRC2002)+1 种基金the China National Postdoctoral Program for Innovative Talents(Grant No.BX20200262)the China Postdoctoral Science Foundation(Grant No.2021M692499)。
文摘GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double heterostructure which introduces an additional p-GaN insertion layer into traditional p-HFETs.The impact of the device structure on the hole densities and valence band energies of both the upper and lower channels is analyzed by using Silvaco TACD simulations,including the thickness of the upper AlGaN layer and the doping impurities and concentration in the GaN buffer layer,as well as the thickness and Mg-doping concentration in the p-GaN insertion layer.With the help of the p-GaN insertion layer,the C-doping concentration in the GaN buffer layer can be reduced,while the density of the two-dimensional hole gas in the lower channel is enhanced at the same time.This work suggests that a double heterostructure with a p-GaN insertion layer is a better approach to improve p-HFETs compared with those devices with C-doped buffer layer alone.
基金financially supported by National Natural Science Foundation of China (Grants Nos. 52273182, 21875122)。
文摘Layered two dimensional(2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites can be obtained by cutting 3D perovskites along < 100 > orientation by incorporation of bulky organic spacers, which play a key role in the performance of 2D perovskite solar cells(PSCs). Compared with aliphatic spacers, aromatic spacers with high dielectric constant have the potential to decrease the dielectric and quantum confinement effect of 2D perovskites, promote efficient charge transport and reduce the exciton binding energy, all of which are beneficial for the photovoltaic performance of 2D PSCs. In this review, we aim to provide useful guidelines for the design of aromatic spacers for 2D perovskites. We systematically reviewed the recent progress of aromatic spacers used in 2D PSCs. Finally, we propose the possible design strategies for aromatic spacers that may lead to more efficient and stable 2D PSCs.
基金supported by the Major State Basic Research Development Program of China(Grant No.2014CB643701)the General Program of the National Natural Science Foundation of China(Grant No.51571064)
文摘The influences of the spacer-layer Ta on the structures and magnetic properties of NdFeB/NdCeFeB multilayer films are investigated via DC sputtering under an Ar pressure of 1.2 Pa. An obvious （00l） texture of the hard phase is observed in each of the films, which indicates that the main phase of the film does not significantly change with Ta spacer-layer thickness. As a result, both the remanence and the saturation magnetization of the magnet first increase and then decrease, and the maximum values of 4π Mr and Hcj are 10.4 kGs （1 Gs=10^-4 T） and 15.0 kOe （1 Oe=79.5775 A·m^-1） for the film with a 2-nm-thick Ta spacer-layer, respectively, where the crystalline structures are columnar shape particles. The measured relationship between irreversible portion D （H）=-△ Mirr/2Mr and H indicates that the nucleation field of the film decreases with spacer layer thickness increasing, owing to slightly disordered grains near the interface between different magnetic layers.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60976008,61006004,61076001,and10979507)the National Basic Research Program of China (Grant No. A000091109-05)the National High Technology Research and Development Program of China (Grant No. 2011AA03A101)
文摘We theoretically study the influence of spacer layer thickness fluctuation（SLTF） on the mobility of a twodimensional electron gas（2DEG） in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer.
文摘An electron transporting material of TFTTP （4-（5-hexylthiophene-2-yl）-2,6-bis（5-trifluoromethyl）thiophen-2-yl）pyridine） was investigated as a cathode buffer layer to enhance the power efficiency of organic solar cells （OSCs） based on subphthalocyanine and C60. The overall power conversion efficiency was increased by a factor of 1.31 by inserting the TFTTP interfacial layer between the active layer and metallic cathode. The inner mechanism responsible for the performance enhancement of OSCs was systematically studied with the simulation of dark diode behavior and optical field distribution inside the devices as well as the characterization of device photocurrent. The results showed that the TFTTP layer could significantly increase the built-in potential in the devices, leading to the enhanced dissociation of charge transfer excitons. In addition, by using TFTTP as the buffer layer, a better Ohmic contact at C60/metal interface was formed, facilitating more efficient free charge carrier collection.
