Umesh Mishra - US grants

The inherent response time of electronic devices can be improved by decreasing the active device capacitance. As devices are scaled laterally using sophisticated lithographic tools, such as e-beam lithography, the devices must also be scaled vertically to ensure proper charge control. This includes the thinning of active channel and contact regions in devices such as FET's and HEMT's. Contact regions, in particular, are difficult to scale by conventional techniques such as ion-implantation. Selective etch-back and regrowth techniques will substantially influence the development of nanometer gate length devices with reduced short channel effects. Using a chemically assisted ion-beam etching system and a regrowth chamber will allow nanometer gate length devices with reduced short channel effects to be fabricated. Vertical devices are exciting because enhanced substrate currents which cause short channel effects in lateral devices are absent. Also, the critical device dimensions are grown by epitaxial techniques and hence can be made extremely small, thereby decreasing electron transit times and enhancing device speed. These and other advanced fabrication techniques will be investigated for use in producing improved performance solid state devices for integrated circuit applications.

Instrumentation will be acquired for the metallo-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) synthesis of III-V nitrides using funds from the Academic Research Infrastructure Program. The major items include a RF heated III-V MOCVD nitride system and a nitrogen plasma source for MBE growth. The aluminum, gallium and indium nitride materials are the most promising materials for optoelectronic devices to operate in the ultraviolet to blue wavelength regime. The research activities will focus on: 1) development of novel epitaxial growth technologies for III-V nitride semiconductors, 2) fundamental studies of the epitaxial growth mechanism, and 3) the fabrication of UV/blue laser diodes, high temperature electronics, and vacuum electronics devices. This research involves substantial support and interest from industrial collaborators. Studies of the epitaxial growth of III-V nitride semiconductors will be conducted with the ultimate objective of producing high quality laser diodes for use in the ultraviolet and blue wavelength regimes. The III-V nitride semiconductors are useful materials for high temperature electronics and also for vacumn electronics devices. The III-V nitrides are technologically important materials for devices, particularly at shorter wavelengths and at higher temperatures.

9528606 Mishra In recent years, vacuum microelectronic devices (VMDs) have become of great interest in the fields such as high speed, high power devices and flat panel displays, because of they combine the advantages of both vacuum tubes and modern semiconductor devices. The key to the success of vacuum microelectronics is the fabrication of the solid-state electron emitters (SSEEs). For applicatimn in flat panel displays, it is required that SSEEs should be stable and generate uniform electron emission with high efficiency and moderate current density. On the other hand, for applications in medium RF power amplifiers and high power RF sources, SSEEs should be very reliable and generate electron emission with high current density. Two types of SSEEs, field emitters 1 and planar emitters 2,3 have been reported in the past with some success. Field emitters, due to its intrinsic nature, have very high emission efficiency and attracted much attention in the field of flat panel displays. Much progress has been made in recent years in the development of field emitters arrays (FEAs) 4, owing to the fast advance of modern semiconductor technologies. In this proposal, we propose a GaN based field emitter and its arrays with an unique fabrication process based on reactive ion etching (RIE) and selective regrowth of GaN point or wedge emitters. ***

Technical Abstract

Research programs in oxides at the University of California, Santa Barbara (UCSB) span a wide range of applications, including as dielectrics, semiconductors, thermoelectrics and memristive devices. Many of these research activities are central to interdisciplinary programs and centers and all support graduate student education and training. These programs require oxide thin films with low defect densities, high purity, compatibility with active electronic device structures, low interface trap states and near-monolayer control over layer thicknesses. To address these needs, we propose to acquire a versatile, state-of-the-art oxide molecular beam epitaxy (MBE) system that will significantly expand capabilities for the synthesis of highly-perfect oxide thin films and structures, as needed to solve key problems in the development of new devices with oxides and in the materials physics of oxide structures. The project will contribute to advancing oxide MBE through the development of approaches to address issues such as stoichiometry control and poor volatility of constituents. In keeping with the tradition of UCSB's MBE Laboratory, the proposed oxide MBE system is designed to facilitate compatibility and accessibility and will be operated as a shared facility, impacting the training of a large number of students in interdisciplinary research programs at UCSB and at collaborating institutions. Graduate students and postdoctoral scholars are the primary users and oxide MBE will be the central focus of many Ph.D. dissertations. Two development engineers provide hands-on training in MBE while formal training is provided by a graduate course and weekly MBE seminars. The oxide MBE system will significantly expand research internship opportunities offered through education programs that target undergraduate and high-school students from underrepresented minority groups.


Non-Technical Abstract

Research programs in oxide materials at the University of California, Santa Barbara (UCSB) span a wide range of applications, such as new electronic devices and energy conversion. Many of these research activities are central to interdisciplinary programs and centers and all support graduate student education and training. These programs require the deposition of thin film oxides with exceptionally low defect densities and high purity, comparable to what is now standard for conventional semiconductor materials. To address these needs, we propose to acquire a versatile, state-of-the-art molecular beam epitaxy (MBE) system for the deposition of thin film oxides. In keeping with the tradition of UCSB's MBE Laboratory, the proposed oxide MBE system will be operated as a shared facility, impacting the education and training of a large number of students in a wide range of interdisciplinary research programs at UCSB and at collaborating institutions. Graduate students and postdoctoral scholars are the primary users. Two development engineers provide hands-on training in MBE while formal training is provided by a graduate course and weekly MBE seminars. The oxide MBE system will significantly expand research internship opportunities offered through education programs that target undergraduate and high-school students from underrepresented minority groups.

The 42nd International Symposium on Compound Semiconductors - 27th International Conference on Indium Phosphide and Related Materials (ISCS/IPRM 2015: Compound Semiconductor Week) covers the field of III-V, II-VI, and IV-IV semiconductors. It addresses III-V and II-VI compound semiconductors as well as SiGe, SiC, and related alloys and has opened up to novel materials such as oxide semiconductors, organic semiconductors and aspects of heterogeneous integration, e.g. of compound semiconductors with Si-based technology. The ISCS series was started in 1966 under the name of "International Symposium on GaAs and Related Compounds" and the current name and co-location with IPRM reflects the broadening of the conference scope due to the wide variety of compound semiconductors vital for modern electronic and optoelectronic devices. This Symposium is expected to have attendance of approximately 300 including attendees from Americas, Europe and Asia. All types of research institutions (academia, government research institutes and industrial laboratories) will be represented. The support funds will be used towards conference proceedings, subsidizing registration fees for students and invited speakers. The timing of this workshop is perfect for this generation of students to learn how the new science and technology of semiconductors is developing. These lessons will be useful beyond semiconductor research, as these students will be able to apply them to any future new materials and technologies that they will encounter during their career.