Enhancement of light extraction in a GaInN light-emitting diode （LED） employing an omni-directional reflector （ODR） consisting of GaN, SnO2 nanorod and an Ag layer was presented. The ODR comprises a transparent, q...Enhancement of light extraction in a GaInN light-emitting diode （LED） employing an omni-directional reflector （ODR） consisting of GaN, SnO2 nanorod and an Ag layer was presented. The ODR comprises a transparent, quarterwave layer of SnO2 nanorod claded by silver and serves as an ohmic contact to p-type GaN. Transparent SnO2 sols were obtained by sol-gel method from SnCl2·2H2O, and SnO2 thin films were prepared by dip-coating technique. The average size of the spherical SnO2 particles obtained is 200 nm. The refractive index of the nanorod SnO2 film layer is 2.01. The GaInN LEDs with GaN/SnO2/Ag ODR show a lower forward voltage. This was attributed to the enhanced reflectivity of the ODR that employs the nanorod SnO2 film layer. Experimental results show that ODR-LEDs have lower optical losses and higher extraction efficiency as compared to conventional LEDs with Ni/Au contacts and conventional LEDs employing a distributed Bragg reflector （DBR）.展开更多
针对SOI(Silicon on Insulator,绝缘体上的硅)高温压力传感器,在真空环境下使用退火的热处理方法,减小了p-Si与Ti/Pt/Au的接触电阻,得到了合适的电阻值和小的比接触电阻率。通过单一因素控制法研究了退火时间和退火温度两个关键因素对...针对SOI(Silicon on Insulator,绝缘体上的硅)高温压力传感器,在真空环境下使用退火的热处理方法,减小了p-Si与Ti/Pt/Au的接触电阻,得到了合适的电阻值和小的比接触电阻率。通过单一因素控制法研究了退火时间和退火温度两个关键因素对样品电阻值和接触表面形貌的影响。采用半导体分析仪、扫描电镜(SEM)和高低温探针台等测试设备以及传输线模型测试方法对样品的欧姆接触性能进行分析,得出了不同温度和时间与欧姆接触的关系。实验结果表明:样品在退火条件为570℃,80 min时电阻的I-V(伏安特性)曲线呈线性,阻值符合设计值,比接触电阻率小,在0～400℃测试环境下电阻值比较稳定。展开更多
With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current （DC） arc jet chemical vapor deposition （CVD） are considered to be one of the most pro...With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current （DC） arc jet chemical vapor deposition （CVD） are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 10^11-10^13 cm-2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method （TLM）. Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10^-5 Ω-cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.展开更多
The Ti/Pt/Au metallization system has an advantage of resisting KOH or TMAH solution etching. To form a good ohmic contact, the Ti/Pt/Au metallization system must be alloyed at 400℃. However, the process temperatures...The Ti/Pt/Au metallization system has an advantage of resisting KOH or TMAH solution etching. To form a good ohmic contact, the Ti/Pt/Au metallization system must be alloyed at 400℃. However, the process temperatures of typical MEMS packaging technologies, such as anodic bonding, glass solder bonding and eutectic bonding, generally exceed 400℃. It is puzzling if the Ti/Pt/Au system is destroyed during the subsequent packaging process. In the present work, the resistance of doped polysilicon resistors contacted by the Ti/Pt/Au metallization system that have undergone different temperatures and time are measured. The experimental results show that the ohmic contacts will be destroyed if heated to 500℃. But if a 20 nm Pt film is sputtered on heavily doped polysilicon and alloyed at 700℃ before sputtering Ti/Pt/Au films, the Pt5 Si2-Ti/Pt/Au metallization system has a higher service temperature of 500℃, which exceeds process temperatures of most typical MEMS packaging technologies.展开更多
Fluorine doped tin oxide （SnO2：F） thin films were prepared on glass substrates by the spray pyrolysis （SP） technique at different substrate temperatures between 380480 ℃. The microstructure of the films was expl...Fluorine doped tin oxide （SnO2：F） thin films were prepared on glass substrates by the spray pyrolysis （SP） technique at different substrate temperatures between 380480 ℃. The microstructure of the films was explored using scanning electron microscope observations. An investigation of selected contacts for the films was performed through the analysis of the I-V measurements which were taken in the dark at room temperature. Indium, aluminum and silver were selected as contacts where two strips of each metal were vacuum-evaporated on the surface of the film. The resistivity of the films was estimated from the linear I-V plots. It was found that the smallest resistivity was obtained using silver contacts, while the largest resistivity was obtained by using indium contacts. This is because silver diffuses in the film and participates in doping, while aluminum and indium cause compensation effects when they diffuse in the film. The best linear fit parameters are those of films with aluminum contacts, and the worst ones are those of films with indium contacts. Annealing was found to improve the electrical properties of the films, especially those deposited at a low substrate temperature. This is because it is expected to encourage crystal growth and to reduce the contact potential which leads to the formation of an alloy. Annealed films are more stable than un-annealed ones.展开更多
The comparative study of epitaxial 380-run-thick p-Al0.091 Ga0.909 N materials without and with special surface chemical treatment is systematically carried out. After the treatment process, the deep level luminous pe...The comparative study of epitaxial 380-run-thick p-Al0.091 Ga0.909 N materials without and with special surface chemical treatment is systematically carried out. After the treatment process, the deep level luminous peak in the 10 K photoluminescence spectrum is eliminated due to the decrease of surface nitrogen vacancy VN related defective sites, while the surface root-mean-square roughness in atomic force microscopy measurement is decreased from 0.395nm to 0.229nm by such a surface preparation method. Furthermore, the performance of surface contact with Ni/Au bilayer metal fihns is obviously improved with the reduction of the Schottky barrier height of 55meV. The x-ray photoelectron spectroscopy （XPS） results show a notable surface element content change after the treatment which is considered to be the cause of the above-mentioned surface characteristics improvement.展开更多
Different-dose phosphorus ion implantation into 4H-SiC followed by high-temperature annealing was investigated.AlN/BN and graphite post-implantation annealing for ion-implanted SiC at 1650℃for 30 min was conducted to...Different-dose phosphorus ion implantation into 4H-SiC followed by high-temperature annealing was investigated.AlN/BN and graphite post-implantation annealing for ion-implanted SiC at 1650℃for 30 min was conducted to electrically activate the implanted P~＋ ions.Ni contacts to the P~＋-implanted 4H-SiC layers were examined by transmission line model and Hall measurements fabricated on P-implanted（0001）.The results indicated that a high-quality ohmic contact and specific contact resistivity of 1.30×10^（-6）Ω·cm^2 was obtained for the P~＋-implanted 4H-SiC layers.TheρC values of the Ni-based implanted layers decreased with increasing P doping concentrations,and a weaker temperature dependence was observed for different samples in the 200-500K temperature range.展开更多
There are several metals that form ohmic contacts for ZnO thin films, such as copper, aluminum and silver. The aim of this work is to make a comparison between these ohmic contacts. To achieve this purpose, polycrysta...There are several metals that form ohmic contacts for ZnO thin films, such as copper, aluminum and silver. The aim of this work is to make a comparison between these ohmic contacts. To achieve this purpose, polycrystalline ZnO thin films were prepared by the spray pyrolysis technique, and characterized by the I-V measurements at room temperature. Two strips of each metal were thermally evaporated on the surface of the film and measurements were first recorded in the dark and room light, then in the dark before and after annealing for A1, which was found to be the best in the set. Films with aluminum contacts gave the smallest resistivity, best ohmicity and they are slightly affected by light as required. On the other hand, copper was found to be the worst, and films with copper contacts gave the largest resistivity, worst ohmicity and they are the most affected by light. Annealing improved the aluminum contacts due to alloying and doping.展开更多
基金the Opening Foundation of China JiLiang University under Grant No.2006KF07
文摘Enhancement of light extraction in a GaInN light-emitting diode （LED） employing an omni-directional reflector （ODR） consisting of GaN, SnO2 nanorod and an Ag layer was presented. The ODR comprises a transparent, quarterwave layer of SnO2 nanorod claded by silver and serves as an ohmic contact to p-type GaN. Transparent SnO2 sols were obtained by sol-gel method from SnCl2·2H2O, and SnO2 thin films were prepared by dip-coating technique. The average size of the spherical SnO2 particles obtained is 200 nm. The refractive index of the nanorod SnO2 film layer is 2.01. The GaInN LEDs with GaN/SnO2/Ag ODR show a lower forward voltage. This was attributed to the enhanced reflectivity of the ODR that employs the nanorod SnO2 film layer. Experimental results show that ODR-LEDs have lower optical losses and higher extraction efficiency as compared to conventional LEDs with Ni/Au contacts and conventional LEDs employing a distributed Bragg reflector （DBR）.
文摘针对SOI(Silicon on Insulator,绝缘体上的硅)高温压力传感器,在真空环境下使用退火的热处理方法,减小了p-Si与Ti/Pt/Au的接触电阻,得到了合适的电阻值和小的比接触电阻率。通过单一因素控制法研究了退火时间和退火温度两个关键因素对样品电阻值和接触表面形貌的影响。采用半导体分析仪、扫描电镜(SEM)和高低温探针台等测试设备以及传输线模型测试方法对样品的欧姆接触性能进行分析,得出了不同温度和时间与欧姆接触的关系。实验结果表明:样品在退火条件为570℃,80 min时电阻的I-V(伏安特性)曲线呈线性,阻值符合设计值,比接触电阻率小,在0～400℃测试环境下电阻值比较稳定。
基金financially supported by the National Natural Science Foundation of China (No. 51272024)the Ph.D. Programs Foundation of the Ministry of Education of China (No. 20110006110011)the Fundamental Research Funds for Central Universities (No. FRF-TP-13-035A)
文摘With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current （DC） arc jet chemical vapor deposition （CVD） are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 10^11-10^13 cm-2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method （TLM）. Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10^-5 Ω-cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.
基金supported by the National Natural Science Foundation of China(No.61376114)
文摘The Ti/Pt/Au metallization system has an advantage of resisting KOH or TMAH solution etching. To form a good ohmic contact, the Ti/Pt/Au metallization system must be alloyed at 400℃. However, the process temperatures of typical MEMS packaging technologies, such as anodic bonding, glass solder bonding and eutectic bonding, generally exceed 400℃. It is puzzling if the Ti/Pt/Au system is destroyed during the subsequent packaging process. In the present work, the resistance of doped polysilicon resistors contacted by the Ti/Pt/Au metallization system that have undergone different temperatures and time are measured. The experimental results show that the ohmic contacts will be destroyed if heated to 500℃. But if a 20 nm Pt film is sputtered on heavily doped polysilicon and alloyed at 700℃ before sputtering Ti/Pt/Au films, the Pt5 Si2-Ti/Pt/Au metallization system has a higher service temperature of 500℃, which exceeds process temperatures of most typical MEMS packaging technologies.
文摘Fluorine doped tin oxide （SnO2：F） thin films were prepared on glass substrates by the spray pyrolysis （SP） technique at different substrate temperatures between 380480 ℃. The microstructure of the films was explored using scanning electron microscope observations. An investigation of selected contacts for the films was performed through the analysis of the I-V measurements which were taken in the dark at room temperature. Indium, aluminum and silver were selected as contacts where two strips of each metal were vacuum-evaporated on the surface of the film. The resistivity of the films was estimated from the linear I-V plots. It was found that the smallest resistivity was obtained using silver contacts, while the largest resistivity was obtained by using indium contacts. This is because silver diffuses in the film and participates in doping, while aluminum and indium cause compensation effects when they diffuse in the film. The best linear fit parameters are those of films with aluminum contacts, and the worst ones are those of films with indium contacts. Annealing was found to improve the electrical properties of the films, especially those deposited at a low substrate temperature. This is because it is expected to encourage crystal growth and to reduce the contact potential which leads to the formation of an alloy. Annealed films are more stable than un-annealed ones.
基金Supported by the National Key Basic Research Special Foundation of China under Grant No T（32000036601, the National High Technology Program of China under Grant Nos 2001AA313130 and 2004AA31G060, the National Natural Science Foundation of China under Crant Nos 60244001 and 60390074, and the Beijing Science and Teclnology Plan （D04040040321）.
文摘The comparative study of epitaxial 380-run-thick p-Al0.091 Ga0.909 N materials without and with special surface chemical treatment is systematically carried out. After the treatment process, the deep level luminous peak in the 10 K photoluminescence spectrum is eliminated due to the decrease of surface nitrogen vacancy VN related defective sites, while the surface root-mean-square roughness in atomic force microscopy measurement is decreased from 0.395nm to 0.229nm by such a surface preparation method. Furthermore, the performance of surface contact with Ni/Au bilayer metal fihns is obviously improved with the reduction of the Schottky barrier height of 55meV. The x-ray photoelectron spectroscopy （XPS） results show a notable surface element content change after the treatment which is considered to be the cause of the above-mentioned surface characteristics improvement.
文摘Different-dose phosphorus ion implantation into 4H-SiC followed by high-temperature annealing was investigated.AlN/BN and graphite post-implantation annealing for ion-implanted SiC at 1650℃for 30 min was conducted to electrically activate the implanted P~＋ ions.Ni contacts to the P~＋-implanted 4H-SiC layers were examined by transmission line model and Hall measurements fabricated on P-implanted（0001）.The results indicated that a high-quality ohmic contact and specific contact resistivity of 1.30×10^（-6）Ω·cm^2 was obtained for the P~＋-implanted 4H-SiC layers.TheρC values of the Ni-based implanted layers decreased with increasing P doping concentrations,and a weaker temperature dependence was observed for different samples in the 200-500K temperature range.
文摘There are several metals that form ohmic contacts for ZnO thin films, such as copper, aluminum and silver. The aim of this work is to make a comparison between these ohmic contacts. To achieve this purpose, polycrystalline ZnO thin films were prepared by the spray pyrolysis technique, and characterized by the I-V measurements at room temperature. Two strips of each metal were thermally evaporated on the surface of the film and measurements were first recorded in the dark and room light, then in the dark before and after annealing for A1, which was found to be the best in the set. Films with aluminum contacts gave the smallest resistivity, best ohmicity and they are slightly affected by light as required. On the other hand, copper was found to be the worst, and films with copper contacts gave the largest resistivity, worst ohmicity and they are the most affected by light. Annealing improved the aluminum contacts due to alloying and doping.
