Improved radio-frequency(RF)power performance of InAlN/GaN high electron mobility transistor(HEMT)is achieved by optimizing the rapid thermal annealing(RTA)process for high-performance low-voltage terminal application...Improved radio-frequency(RF)power performance of InAlN/GaN high electron mobility transistor(HEMT)is achieved by optimizing the rapid thermal annealing(RTA)process for high-performance low-voltage terminal applications.By optimizing the RTA temperature and time,the optimal annealing condition is found to enable low parasitic resistance and thus a high-performance device.Besides,compared with the non-optimized RTA HEMT,the optimized one demonstrates smoother ohmic metal surface morphology and better heterojunction quality including the less degraded heterojunction sheet resistance and clearer heterojunction interfaces as well as negligible material out-diffusion from the barrier to the channel and buffer.Benefiting from the lowered parasitic resistance,improved maximum output current density of 2279 mA·mm^(-1)and higher peak extrinsic transconductance of 526 mS·mm^(-1)are obtained for the optimized RTA HEMT.In addition,due to the superior heterojunction quality,the optimized HEMT shows reduced off-state leakage current of 7×10^(-3)mA·mm^(-1)and suppressed current collapse of only 4%,compared with those of 1×10^(-1)mA·mm^(-1)and 15%for the non-optimized one.At 8 GHz and V_(DS)of 6 V,a significantly improved power-added efficiency of 62%and output power density of 0.71 W·mm^(-1)are achieved for the optimized HEMT,as the result of the improvement in output current,knee voltage,off-state leakage current,and current collapse,which reveals the tremendous advantage of the optimized RTA HEMT in high-performance low-voltage terminal applications.展开更多
Chinese college students have some drawbacks in English learning and mastering. Through a dozen years of English learning, some of them have high ability of passing examinations, but the practical application ability ...Chinese college students have some drawbacks in English learning and mastering. Through a dozen years of English learning, some of them have high ability of passing examinations, but the practical application ability is barely satisfactory with relatively poor listening level and oral expression ability. The objective cause for this situation is the relatively single and stylization English teaching model used by traditional colleges and universities. This model only emphasizes learning on class which greatly harms students＇ English learning enthusiasm and initiatives. The result is that although the students passed CET4 and CET6 long time before their graduation, they still not dare to open their mouth to speaking concerning face to face English communications. Over the years, the researches on how to improve college students＇ English application ability never stop and they did obtain some achievements and show some opportunities, for example, if we can bring APP （application programs） into college English listening class, it will largely meet students requirements on English learning and this can also replenish and perfect traditional English teaching model.展开更多
This paper analyzes the communication business needs and application characteristics based on China's railway operation scenarios.Focusing on the specific needs of railways,the 5G-Railway(5G-R)system adds railway-...This paper analyzes the communication business needs and application characteristics based on China's railway operation scenarios.Focusing on the specific needs of railways,the 5G-Railway(5G-R)system adds railway-specific functional network elements on the basis of general architecture.In terms of system networking,it focuses on the innovative key technologies of 5G-R core network and wireless network networking to adapt to the railway management mechanism and reliability requirements.It analyzes the technical optimization and innovation of 5G-R railway common equipment in terms of redundancy mode,function sinking,fault detection and reversal mechanism,etc.;5G-R wireless network adopts the same-site equipment redundancy mode,and the paper analyzes the technological innovation of RRU redundancy,BBU redundancy and PCI planning,etc.;it also highlights the benefits of the train-ground integrated transmission system,including reduced roof antennas,decoupling of services and communication,unified spatial and temporal benchmarks,and cost savings.展开更多
基金Project supported by the National Key Research and Development Project of China (Grant No.2021YFB3602404)part by the National Natural Science Foundation of China (Grant Nos.61904135 and 62234009)+4 种基金the Key R&D Program of Guangzhou (Grant No.202103020002)Wuhu and Xidian University special fund for industry-university-research cooperation (Grant No.XWYCXY-012021014-HT)the Fundamental Research Funds for the Central Universities (Grant No.XJS221110)the Natural Science Foundation of Shaanxi,China (Grant No.2022JM-377)the Innovation Fund of Xidian University (Grant No.YJSJ23019)。
文摘Improved radio-frequency(RF)power performance of InAlN/GaN high electron mobility transistor(HEMT)is achieved by optimizing the rapid thermal annealing(RTA)process for high-performance low-voltage terminal applications.By optimizing the RTA temperature and time,the optimal annealing condition is found to enable low parasitic resistance and thus a high-performance device.Besides,compared with the non-optimized RTA HEMT,the optimized one demonstrates smoother ohmic metal surface morphology and better heterojunction quality including the less degraded heterojunction sheet resistance and clearer heterojunction interfaces as well as negligible material out-diffusion from the barrier to the channel and buffer.Benefiting from the lowered parasitic resistance,improved maximum output current density of 2279 mA·mm^(-1)and higher peak extrinsic transconductance of 526 mS·mm^(-1)are obtained for the optimized RTA HEMT.In addition,due to the superior heterojunction quality,the optimized HEMT shows reduced off-state leakage current of 7×10^(-3)mA·mm^(-1)and suppressed current collapse of only 4%,compared with those of 1×10^(-1)mA·mm^(-1)and 15%for the non-optimized one.At 8 GHz and V_(DS)of 6 V,a significantly improved power-added efficiency of 62%and output power density of 0.71 W·mm^(-1)are achieved for the optimized HEMT,as the result of the improvement in output current,knee voltage,off-state leakage current,and current collapse,which reveals the tremendous advantage of the optimized RTA HEMT in high-performance low-voltage terminal applications.
文摘Chinese college students have some drawbacks in English learning and mastering. Through a dozen years of English learning, some of them have high ability of passing examinations, but the practical application ability is barely satisfactory with relatively poor listening level and oral expression ability. The objective cause for this situation is the relatively single and stylization English teaching model used by traditional colleges and universities. This model only emphasizes learning on class which greatly harms students＇ English learning enthusiasm and initiatives. The result is that although the students passed CET4 and CET6 long time before their graduation, they still not dare to open their mouth to speaking concerning face to face English communications. Over the years, the researches on how to improve college students＇ English application ability never stop and they did obtain some achievements and show some opportunities, for example, if we can bring APP （application programs） into college English listening class, it will largely meet students requirements on English learning and this can also replenish and perfect traditional English teaching model.
文摘This paper analyzes the communication business needs and application characteristics based on China's railway operation scenarios.Focusing on the specific needs of railways,the 5G-Railway(5G-R)system adds railway-specific functional network elements on the basis of general architecture.In terms of system networking,it focuses on the innovative key technologies of 5G-R core network and wireless network networking to adapt to the railway management mechanism and reliability requirements.It analyzes the technical optimization and innovation of 5G-R railway common equipment in terms of redundancy mode,function sinking,fault detection and reversal mechanism,etc.;5G-R wireless network adopts the same-site equipment redundancy mode,and the paper analyzes the technological innovation of RRU redundancy,BBU redundancy and PCI planning,etc.;it also highlights the benefits of the train-ground integrated transmission system,including reduced roof antennas,decoupling of services and communication,unified spatial and temporal benchmarks,and cost savings.
