My goal is to become a proficient researcher on advanced materials such as 2Dmaterials and III-V materials due to the following reasons. Firstly, in the era of postMoore’slaw, these materials have become increasingly important for their applicationin either the trend of “More than Moore” or “Beyond CMOS”.
Secondly, I plan todedicate myself to the development of semiconductor devices owing to my enthusiasmat research. Therefore, to fulfill my goal, I am writing for applying the Ph.D.
programin EE at Yale University, which will be the best choice for me due to your eminentacademic achievement and highly esteemed reputation.The undergraduate study in Material Science and Engineering (MSE) provided mewith not only views of material properties such as lattice structures and grain boundaries,but also methods of material characterization like AFM, Raman spectroscopy, SEM andTEM. Among all curriculum, I was most interested in the courses relevant to solid-stateelectronics. After taking the courses instructed by Prof. Miin-Jang Chen, I wasfascinated by semiconductor devices and their industrial application. Hence, I took thespecial project course by Prof. Chen and learned the process of atomic layer deposition(ALD). To further extend my knowledge, I applied for Graduate Institute of Photonicsand Optoelectronics at National Taiwan University (NTU) and joined Prof.
Chao-HsinWu’s research group.In Prof. Wu’s group, I equipped myself with abilities to measure the electricalcharacteristics, analyze the results and fabricate semiconductor devices. In Si FinFETsproject, I learned the principles of electrical measurement and measured I-Vcharacteristics of Si FinFETs at room and cryogenic temperatures. Totally 240 deviceswith multiple geometry were measured, where on current, mobility, subthreshold swingand drain induced barrier lowering (DIBL) were systematically analyzed. On the otherhand, I became skillful with device fabrication process and familiar with the workingprinciples of GaN High Electron Mobility Transistors (HEMTs). I was able to completethe devices by photolithography, metal deposition and rapid thermal annealing.
Inaddition, I studied the principle of Ohmic contacts formation for GaN HEMTs andtheories of transfer length method (TLM), and extracted the contact resistance frompractical devices.Furthermore, I exhibited my capability to research comprehensively in the 2Dmaterials project collaborated with Taiwan Semiconductor Manufacturing Company(TSMC) and achieved great academic results. In developing BP transistors, I producedand transferred few-layered BP by mechanical exfoliation, and then used electron-beamlithography to define the patterns followed by metal deposition and lift-off process. After several refinement of the experiments, I successfully demonstrated a blackphosphorus transistor with a high hole mobility of 340 cm2/Vs.
In improving metalcontacts of BP transistors, I devoted myself to developing a novel doping methodenabling metallic Ohmic contacts to be formed at source/drain (S/D) region. After atotal number of thirty meetings with Dr. Yu-Ming Lin, a deputy director in TSMC, arecord low contact resistance of 0.365 k???m was achieved and metallic propertieswere demonstrated. Moreover, the results were published in Scientific Reports andsuccessfully applied for a patent. In developing 2D heterostructures, I built up a 2Dheterostructure stacking process by myself.
Taking advantage of this technique, Istacked graphene/MoS2 heterostructures, where graphene served as the leading contactsto MoS2 channel, thus achieving a high mobility of 116 cm2/Vs by improving S/Dcontacts. The results were published in AIP Advances. In addition, the heterostructuresof graphene-contact MoS2 fully encapsulated by top and bottom h-BN demonstratedthe improvement of mobility and hysteresis.In the project of 2D materials, I also enhanced my ability to solve problemsencountered in the research. For instance, when investigating metal/BP contacts, Idiscovered the deviation in extracting Schottky barrier height (SBH) and proposed amodified method with a more reasonable value. The results were submitted to Journalof Physics D: Applied Physics. To develop 2D heterostructures, I also set up ahomemade station, where 2D materials can be finely stacked within a short time.Furthermore, to improve contact resistance of BP transistors, I figured out a process notonly achieving metallic doping at S/D region but also improving overall electricalperformance including ION/IOFF ratio, on current and mobility.
Most importantly, I found my enthusiasm at research on advanced materials in mygraduate study. After accomplishing some great works on 2D materials, I craved formore insights and breakthroughs to make more contributions to semiconductor industry.Advanced materials such as III-V materials, 2D materials and germanium are promisingdue to their highly regarded potential for future application, and can thus gratify myattempts.In sum, I hope to continue the research at your graduate school becauseDepartment of EE at Yale University is consistently a worldwide top-ranked EE schoolwith not only complete and advanced facilities, but also tremendous academicachievements, and best of all, the extraordinary faculties. I am particularly interested inthe academic works by Prof.
Fengnian Xia, who has achieved outstanding results inelectronics of 2D materials. The work on synthesis of thin-film BP by Prof. Xia is alsoimpressing, which plays an important role in industrial application of BP. Mostimportantly, I believe I am an ideal candidate for your school. After the training at NTU,I am confident that I am well qualified and can independently execute a research project with my ability to fix problems.
With proficient skills and professional attitudes, I alsobelieve I can quickly involve myself into the research and make contributionsimmediately. Furthermore, my motivation to investigate into the semiconductor fieldsis intense. I will be very honored to study at one of the best EE schools, which willenable me to reach my goal.