High-quality AlN epitaxial layers with low dislocation densities and uniform crystal quality are essential for next-gener-ation optoelectronic and power devices.This study reports the epitaxial growth of 6-inch AlN fi...High-quality AlN epitaxial layers with low dislocation densities and uniform crystal quality are essential for next-gener-ation optoelectronic and power devices.This study reports the epitaxial growth of 6-inch AlN films on 17 nm AlN/sapphire tem-plates using metal-organic chemical vapor deposition(MOCVD).Comprehensive characterization reveals significant advance-ments in crystal quality and uniformity.Atomic force microscopy(AFM)shows progressive surface roughness reduction during early growth stages,achieving stabilization at a root mean square(RMS)roughness of 0.216 nm within 3 min,confirming suc-cessful 2D growth mode.X-ray rocking curve(XRC)analysis indicates a marked reduction in the(0002)reflection full width at half maximum(FWHM),from 445 to 96 arcsec,evidencing effective dislocation annihilation.Transmission electron microscopy(TEM)demonstrates the elimination of edge dislocations near the AlN template interface.Stress analysis highlights the role of a highly compressive 17 nm AlN template(5.11 GPa)in facilitating threading dislocation bending and annihilation,yielding a final dislocation density of~1.5×10^(7) cm^(-2).Raman spectroscopy and XRC mapping confirm excellent uniformity of stress and crystal quality across the wafer.These findings demonstrate the feasibility of this method for producing high-quality,large-area,atomically flat AlN films,advancing applications in optoelectronics and power electronics.展开更多
We have investigated homoepitaxy of Al N films grown by molecular beam epitaxy(MBE)on Al N/sapphire templates.The MBE epitaxy of Al N at the low temperature range,which is suitable for Al Ga N,encounters significant c...We have investigated homoepitaxy of Al N films grown by molecular beam epitaxy(MBE)on Al N/sapphire templates.The MBE epitaxy of Al N at the low temperature range,which is suitable for Al Ga N,encounters significant challenge in preventing Al droplet and pits,since the migration and desorption rate of Al atom are very low.In contrast,by elevating the growth temperature,such a difficulty can be effectively overcome,and we were able to grow Al N films with much improved surface morphology and obtained step flow growth mode without any Al droplets and pits.The cathodoluminescence spectroscopy indicate that the impurity incorporation and defect generation in the Al N epilayers was suppressed by elevating the growth temperature.A systematic investigation on the influence of Al beam flux and growth temperature in a very wide range on the Al N films has been conducted,and a comprehensive growth diagram of MBE Al N has been obtained.展开更多
This study investigates the gate leakage mechanisms of AlN/GaN metal–insulator–semiconductor high-electronmobility transistors(MIS-HEMTs)fabricated on silicon substrate with Al_(2)O_(3)/SiN as stacked gate dielectri...This study investigates the gate leakage mechanisms of AlN/GaN metal–insulator–semiconductor high-electronmobility transistors(MIS-HEMTs)fabricated on silicon substrate with Al_(2)O_(3)/SiN as stacked gate dielectrics,analyzing behaviors across high and low temperature conditions.In the high-temperature reverse bias region(T>275 K,V_(G)<0 V),Poole–Frenkel emission(PFE)dominates at low electric fields,while trap-assisted tunneling(TAT)is the primary mechanism at medium to high electric fields.The shift from PFE to TAT as the dominant conduction mechanism is due to the increased tunneling effect of electrons as the electric field strength rises.Additionally,TAT is found to be the main gate leakage mechanism under low-temperature reverse bias(T<275 K,V_(G)<0 V).At lower temperatures,the reduction in electron energy causes the emission process to rely more on electric field forces.Furthermore,under forward bias conditions at both high and low temperatures(225 K<T<375 K,V_(G)>0 V),conduction is primarily dominated by defect-assisted tunneling(DAT).展开更多
在蓝宝石衬底上生长一层AlN缓冲层是LED芯片提升器件质量的常用手段,其薄膜质量与器件整体性能息息相关。为了进一步提高AlN薄膜的结晶质量,本文首先使用PVD、HTA以及MOCVD方法对蓝宝石衬底上的AlN薄膜进行制备,制备出了高结晶质量的Al...在蓝宝石衬底上生长一层AlN缓冲层是LED芯片提升器件质量的常用手段,其薄膜质量与器件整体性能息息相关。为了进一步提高AlN薄膜的结晶质量,本文首先使用PVD、HTA以及MOCVD方法对蓝宝石衬底上的AlN薄膜进行制备,制备出了高结晶质量的AlN薄膜。随后引入不同的c/m衬底斜切角去探索斜切角度对薄膜结晶质量的影响。最终成功在c面蓝宝石衬底上制备出1 μm的摇摆曲线半高宽51 arcsec,表面粗糙度为0.987 nm的高质量c轴取向的AlN薄膜。并通过对比不同衬底斜切角的形貌特征变化,认为造成结晶质量提升的原因是一种由衬底斜切角诱导的台阶终止位错的机制。在此基础上,对不同衬底斜切角的AlN薄膜进行了UV光学性能的表征,通过紫外透过率实验证实了0.2˚的c/m衬底斜切角确实给薄膜的性能带来了提升,其紫外透过率和光学禁带宽度都有了一定程度的提升,最终达到了80%透过率,6.09 eV光学带隙的优异性能。A layer of AlN buffer on a sapphire substrate is a common method for improving the device quality of LED chips, and the quality of the film is closely related to the overall performance of the device. In order to further enhance the crystallinity of AlN films, this study first employs PVD, HTA, and MOCVD methods to fabricate AlN films on sapphire substrates, achieving AlN films with high crystallinity. Subsequently, different offcut angles of the c/m substrates are introduced to explore the impact of the offcut angle on the crystallinity of the films. As a result, high-quality c-axis oriented AlN films with a rocking curve full width at half maximum (FWHM) of 51 arcseconds and a surface roughness of 0.987 nm were successfully prepared on c-plane sapphire substrates. By comparing the morphological changes of films with different substrate offcut angles, it is proposed that the improvement in crystallinity is due to a mechanism where the substrate offcut angle induces the termination of step-edge dislocations. Based on this, UV optical performance of AlN films with different substrate offcut angles was characterized. Ultraviolet transmittance experiments confirmed that a 0.2˚ c/m substrate offcut angle indeed enhanced the performance of the films, resulting in an improvement in both the UV transmittance and optical bandgap. Ultimately, an 80% transmittance and a 6.09 eV optical bandgap were achieved, demonstrating excellent performance.展开更多
Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by...Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.展开更多
提高城市电动出租车充电站规划布局的科学性和充电站的使用效率对减少司机的时间成本、推动绿色出行有重要意义。首先模拟电动出租车营运过程,得到随机充电需求点;其次,利用Dijkstra算法和排队仿真模型模拟出租车寻找充电站和等待充电...提高城市电动出租车充电站规划布局的科学性和充电站的使用效率对减少司机的时间成本、推动绿色出行有重要意义。首先模拟电动出租车营运过程,得到随机充电需求点;其次,利用Dijkstra算法和排队仿真模型模拟出租车寻找充电站和等待充电的过程,以寻站时间、排队等待时间和流失成本最小化作为目标函数,建立充电站选址优化模型。并使用改进的自适应大规模邻域搜索(adaptive large neighborhood search,ALNS)算法求解模型。实验结果表明,改进的ALNS算法具有较好的性能,总时间成本最低,且充电站选择位置和充电桩数量较为合理。展开更多
基金supported by National Key R&D Program of China(2022YFB3605100)the National Science Fund for Distinguished Young Scholars of China(62425408)+5 种基金the National Natural Science Foundation of China(62204241,U22A2084,and 62121005)Key Research and Development Projects of Jilin Provincial Science and Technology Development Plan(20240302027GX)the Natural Science Foundation of Jilin Province(20230101345JC,20230101360JC,20230101107JC)the Youth Innovation Promotion Association of CAS(2023223)the Young Elite Scientist Sponsorship Program By CAST(YESS20200182)the CAS Talents Program.
文摘High-quality AlN epitaxial layers with low dislocation densities and uniform crystal quality are essential for next-gener-ation optoelectronic and power devices.This study reports the epitaxial growth of 6-inch AlN films on 17 nm AlN/sapphire tem-plates using metal-organic chemical vapor deposition(MOCVD).Comprehensive characterization reveals significant advance-ments in crystal quality and uniformity.Atomic force microscopy(AFM)shows progressive surface roughness reduction during early growth stages,achieving stabilization at a root mean square(RMS)roughness of 0.216 nm within 3 min,confirming suc-cessful 2D growth mode.X-ray rocking curve(XRC)analysis indicates a marked reduction in the(0002)reflection full width at half maximum(FWHM),from 445 to 96 arcsec,evidencing effective dislocation annihilation.Transmission electron microscopy(TEM)demonstrates the elimination of edge dislocations near the AlN template interface.Stress analysis highlights the role of a highly compressive 17 nm AlN template(5.11 GPa)in facilitating threading dislocation bending and annihilation,yielding a final dislocation density of~1.5×10^(7) cm^(-2).Raman spectroscopy and XRC mapping confirm excellent uniformity of stress and crystal quality across the wafer.These findings demonstrate the feasibility of this method for producing high-quality,large-area,atomically flat AlN films,advancing applications in optoelectronics and power electronics.
基金Project supported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0303400)the National Key Research and Development Program of China(Grant Nos.2022YFB3605602 and 2024YFE0205000)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20243037)the Jiangsu Special Professorship,Collaborative Innovation Center of Solid-state Lighting and Energy-saving Electronics,Postdoctoral Fellowship Program of CPSF(Grant No.GZC20231098)。
文摘We have investigated homoepitaxy of Al N films grown by molecular beam epitaxy(MBE)on Al N/sapphire templates.The MBE epitaxy of Al N at the low temperature range,which is suitable for Al Ga N,encounters significant challenge in preventing Al droplet and pits,since the migration and desorption rate of Al atom are very low.In contrast,by elevating the growth temperature,such a difficulty can be effectively overcome,and we were able to grow Al N films with much improved surface morphology and obtained step flow growth mode without any Al droplets and pits.The cathodoluminescence spectroscopy indicate that the impurity incorporation and defect generation in the Al N epilayers was suppressed by elevating the growth temperature.A systematic investigation on the influence of Al beam flux and growth temperature in a very wide range on the Al N films has been conducted,and a comprehensive growth diagram of MBE Al N has been obtained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62188102,62174125,and 62131014).
文摘This study investigates the gate leakage mechanisms of AlN/GaN metal–insulator–semiconductor high-electronmobility transistors(MIS-HEMTs)fabricated on silicon substrate with Al_(2)O_(3)/SiN as stacked gate dielectrics,analyzing behaviors across high and low temperature conditions.In the high-temperature reverse bias region(T>275 K,V_(G)<0 V),Poole–Frenkel emission(PFE)dominates at low electric fields,while trap-assisted tunneling(TAT)is the primary mechanism at medium to high electric fields.The shift from PFE to TAT as the dominant conduction mechanism is due to the increased tunneling effect of electrons as the electric field strength rises.Additionally,TAT is found to be the main gate leakage mechanism under low-temperature reverse bias(T<275 K,V_(G)<0 V).At lower temperatures,the reduction in electron energy causes the emission process to rely more on electric field forces.Furthermore,under forward bias conditions at both high and low temperatures(225 K<T<375 K,V_(G)>0 V),conduction is primarily dominated by defect-assisted tunneling(DAT).
文摘在蓝宝石衬底上生长一层AlN缓冲层是LED芯片提升器件质量的常用手段,其薄膜质量与器件整体性能息息相关。为了进一步提高AlN薄膜的结晶质量,本文首先使用PVD、HTA以及MOCVD方法对蓝宝石衬底上的AlN薄膜进行制备,制备出了高结晶质量的AlN薄膜。随后引入不同的c/m衬底斜切角去探索斜切角度对薄膜结晶质量的影响。最终成功在c面蓝宝石衬底上制备出1 μm的摇摆曲线半高宽51 arcsec,表面粗糙度为0.987 nm的高质量c轴取向的AlN薄膜。并通过对比不同衬底斜切角的形貌特征变化,认为造成结晶质量提升的原因是一种由衬底斜切角诱导的台阶终止位错的机制。在此基础上,对不同衬底斜切角的AlN薄膜进行了UV光学性能的表征,通过紫外透过率实验证实了0.2˚的c/m衬底斜切角确实给薄膜的性能带来了提升,其紫外透过率和光学禁带宽度都有了一定程度的提升,最终达到了80%透过率,6.09 eV光学带隙的优异性能。A layer of AlN buffer on a sapphire substrate is a common method for improving the device quality of LED chips, and the quality of the film is closely related to the overall performance of the device. In order to further enhance the crystallinity of AlN films, this study first employs PVD, HTA, and MOCVD methods to fabricate AlN films on sapphire substrates, achieving AlN films with high crystallinity. Subsequently, different offcut angles of the c/m substrates are introduced to explore the impact of the offcut angle on the crystallinity of the films. As a result, high-quality c-axis oriented AlN films with a rocking curve full width at half maximum (FWHM) of 51 arcseconds and a surface roughness of 0.987 nm were successfully prepared on c-plane sapphire substrates. By comparing the morphological changes of films with different substrate offcut angles, it is proposed that the improvement in crystallinity is due to a mechanism where the substrate offcut angle induces the termination of step-edge dislocations. Based on this, UV optical performance of AlN films with different substrate offcut angles was characterized. Ultraviolet transmittance experiments confirmed that a 0.2˚ c/m substrate offcut angle indeed enhanced the performance of the films, resulting in an improvement in both the UV transmittance and optical bandgap. Ultimately, an 80% transmittance and a 6.09 eV optical bandgap were achieved, demonstrating excellent performance.
基金supported by the National Key Research and Development Program of China(No.2021YFA0715600)the National Natural Science Foundation of China(Nos.62274125,52192611)+2 种基金the Guangdong Basic and Applied Basic Research Fund(No.2023A1515030084)the Key Research and Development Program of Shaanxi Province(Grant No.2024GX-YBXM-410)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202220).
文摘Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.
文摘提高城市电动出租车充电站规划布局的科学性和充电站的使用效率对减少司机的时间成本、推动绿色出行有重要意义。首先模拟电动出租车营运过程,得到随机充电需求点;其次,利用Dijkstra算法和排队仿真模型模拟出租车寻找充电站和等待充电的过程,以寻站时间、排队等待时间和流失成本最小化作为目标函数,建立充电站选址优化模型。并使用改进的自适应大规模邻域搜索(adaptive large neighborhood search,ALNS)算法求解模型。实验结果表明,改进的ALNS算法具有较好的性能,总时间成本最低,且充电站选择位置和充电桩数量较为合理。
