| Low Noise Amplifiers Based on Lattice Engineered Substrates |
01 NOV 2004 |
117 pages |
| Authors:
James S. Speck; Umesh K. Mishra; CALIFORNIA UNIV REGENTS SANTA BARBARA OFFICE OF RESEARCH
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 | In this program we are developing novel strain relaxed templates for device applications including low noise amplifiers. The approach we are investigating utilizes the process of relaxation of a coherent hypercritical thickness strained semiconductor overlayer (e.g., InGaAs). In the first two years of this program, we had focused on the relaxation of a strained layer in direct contact with an oxidizing Al containing semiconductor (AlAs or AlGaAs). In the third ... |
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| Uncooled RF Electronics for Airborne Radar |
AUG 2003 |
13 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Improvements to the AlGaN/GaN HEMT device technology was studied at the epitaxial level by MOCVD, aimed at enhancing efficiency and linearity. A number of projects were performed under the program, including reducing the contact resistance, introducing a type of contacts that permits very short access regions, introducing hot electron launching into the channel, and double channel structures. Basic research in support of these projects was also performed, including studies of ... |
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| High Power Broadband Amplifiers for 1-18 GHz Naval Radar |
JUN 2002 |
32 pages |
| Authors:
Mark Rodwell; Umesh K. Mishra; CALIFORNIA UNIV SANTA CRUZ
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| Three generations of dual-gate AlGaN/GaN HEMTs on sapphire were fabricated and characterized. First generation dual-gate HEMT had equal gate lengths of 650 nm produced through stepper lithography. Current gain cut-off frequency (f sub tau)) of 20 GHz, 60 V breakdown, 11 dB small-signal gain, 2.5 W/mm saturated output power, and 35% power added efficiency (PAE) at 4 GHz were achieved. Second and third generation dual-gate HEMT had unequal gate lengths ... |
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| Current Apertured Vertical Electron Transistor (CAVET) |
DEC 2001 |
14 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA
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| We have demonstrated the first GaN current aperture vertical electron transistor (CAVET). A 2 micrometer thick GaN:Si drain region followed by a 0.4 micrometer GaN:Fe insulating layer and an 800 Angstrom unintentionally doped GaN cap were grown by MOCVD on a c-plane sapphire substrate. Channel apertures were etched, and a maskless regrowth was performed to grow conducting GaN inside the channel as well as to thicken the UID GaN above ... |
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| Wideband Transferred-Substrate AlGaN-GaN Heterojunction Bipolar Transistors for Microwave Power Applications |
JAN 2001 |
10 pages |
| Authors:
Umesh K. Mishra; Lee McCarthy; CALIFORNIA UNIV SANTA BARBARA
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| This report reviews efforts to develop growth and fabrication technology for the GaN HBT at UCSB. Conventional devices are grown by plasma assisted MBE on MOCVD GaN templates on sapphire and fully MOCVD devices. HBTs were also fabricated on LEO material identifying threading dislocations as the primary source of collector-emitter leakage which was reduced by 4 orders of magnitude for devices on non-dislocated material. Base doping studies show that the ... |
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| Inductively Coupled Plasma System (ICP) |
2001 |
4 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| This is the final technical report for contract number F49620-01-1- 0307 with the Air Force Office of Scientific Research. The report provides information about the inductively coupled plasma system that was acquired under this contract. The system is a Unaxis Versalock 700, a production level cluster tool for dry etch and dielectric deposition. The tool provides up to 3 process chambers. Currently two of them are in function in our ... |
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| Center for Non-Stoichiometric Semiconductors |
SEP 2000 |
68 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Research under the PRET program has covered a varied range of materials and device applications. Early work was directed mostly toward understanding and implementing low-temperature grown (LTG) GaAs into field- effect transistors (FETs) providing increased breakdown voltages and a reduced noise performance. In recent years the research has been redirected into the newly emerging area of oxides and oxide electronics. Oxide produced from the ... |
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| Uncooled RF Electronics for Airborne Radar. AlGaN/GaN HEMT Structure Development by MBE |
31 JUL 1999 |
11 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA
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| Using MBE efforts, concentration was focused on the homoepitaxial growth of HEMT nitride-based structures on high quality MOCVD templates grown on (0001) sapphire substrates, allowing the avoidance of the sapphire nucleation step and thus the high dislocation and extended defect density that can occur with direct MBE growth on sapphire. |
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| Investigation of the Electronic and Structural Properties of Oxidized- A1As/GaAs Interfaces |
30 JUN 1999 |
24 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA
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| Research involving devices incorporating oxides formed by the wet oxidation of Al(Ga)As and AlAs0.56Sb0.44 has been performed. Previous results from research on GaAs-On-Insulator (GOI) MESFETs suggested a correlation between channel electronic characteristics, oxidation, and buffer layer. In our research it was found that devices with high aluminum composition LT AlGaAs buffers maintained better channel characteristics after oxidation. In addition to MESFETs, preliminary work into high-speed HBTs was also performed. Base- ... |
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| Non-Cesiated Solid State Electron Emitters (Cold Cathodes) & Their Applications in Vacuum Microelectronics |
31 MAY 1999 |
25 pages |
| Authors:
Umesh K. Mishra; Robert D. Underwood; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Stable, non-cesiated cold cathodes hold much promise for high power and high efficiency vacuum electronics. Cesium is typically used to lower the surface barrier to electron emission, but cesium presents problems with reliability and lifetime. GaN-based cold cathodes have the advantage of having a low surface barrier and a stable surface, both of which are beneficial for cold cathode electron emission. Better performance, in terms of ... |
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| Center for the Radiation Studies and Solutions |
1999 |
115 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA
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| The influence of the radiation to the performance of the GaN-based and GaAs-based electronic devices was investigated extensively. In order to study the effects upon various devices, several novel device structures (such as p-capped AlGaN/GaN HEMTs and GOI GaAs pHEMTs) as well as new processing techniques were developed. The radiation induced traps, the forward and reserved biased currents of the diodes and the DC current-voltage characteristics of HEMTs and HBTs ... |
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| Characterization of (Al,Ga,In)N Grown Using Lateral Epitaxial Overgrowth |
AUG 1998 |
12 pages |
| Authors:
Umesh K. Mishra; Steven P. DenBaars; CALIFORNIA UNIV SANTA BARBARA
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| We describe the effect of various growth parameters such as V/III ratio and temperature on the lateral epitaxial overgrowth of GaN by MOCVD. We also discuss the effect of the mask pattern geometry used as the "seed" template. Structural characterization (AFM, TEM) show that for suitable growth conditions the LEO GaN contains almost no threading dislocations (approx. 10 (exp 5)/sq cm). Based on these results ... |
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| A Novel mm-Wave Heterojunction JFET Technology with Suppressed Hole Injection |
SEP 96 |
185 pages |
| Authors:
Umesh K. Mishra; Jeffrey B. Shealy; CALIFORNIA UNIV SANTA BARBARA
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| We have developed a device technology using n-AlInAs/GaInAs on InP substrates, where the gate technology incorporates a p-n junction barrier. The p-n junction exists between an undepleted p-type surface layer (p(+)-GaInAs) and the two-dimensional electron gas (2DEC) in the GaInAs channel. The p(+)-2DEG junction provides a sufficiently high gate barrier that exhibits low gate leakage current and a high breakdown voltage. At the same time, the fixed gate- to-channel separation ... |
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| The Study of the Materials Properties of LTG (Al) GaAs and its Electronic and Opto-Electronic Device Applications |
14 NOV 95 |
23 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| GaAs based semiconductors grown at a low temperature (LIG) by MBE have |
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| High Power, High Efficiency MESFETs and HEMTs |
14 JUN 95 |
8 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| For the duration of the project dated above, the work on the AASERT program concentrated on improving the power performance of GaAs MESFETs with LTG GaAs surface passivation layers by studying the effects of source and drain contacts regrown by MOCVD on both device breakdown and gain. |
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| A Novel mm-Wave Heterojunction JFET Technology with Suppressed Hole Injection |
JUN 95 |
13 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| It is necessary for a good compound semiconductor device technology to be simple and relatively transparent to the two commercially important families of materials namely GaAs and lnP based. The technology should be uniform, high performance and low cost to penetrate crucial large volume markets. The lack of a large bandgap insulator (with low surface states) in III- V materials eliminates the choice of an insulator gate technology. Further, lnP ... |
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| Vacuum Microelectronic Emitters and Their Applications Using Compound Semiconductor Technology |
16 JUL 94 |
29 pages |
| Authors:
David Holcombe; Wei-Nan Jiang; Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Vacuum microelectronic devices (VMDs) are a class of devices in which electron transport occurs both in semiconductors and in vacuum. They have the potential of combining the advantages of vacuum tube based devices with those of modern semiconductor devices. The key to the success of VMDs is fabricating reliable solid state electron emitters with high emission efficiency and high emission current density. This report will present the design, growth, fabrication ... |
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| Vacuum Microelectronic Emitters and Their Applications Using Compound Semiconductor Technology |
16 JUL 94 |
29 pages |
| Authors:
David Holcombe; Wei-Nan Jiang; Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Vacuum microelectronic devices (VMDs) are a class of devices in which electron transport occurs both in semiconductors and in vacuum. They have the potential of combining the advantages of vacuum tube based devices with those of modern semiconductor devices. The key to the success of VMDs is fabricating reliable solid state electron emitters with high emission efficiency and high emission current density. This report will present the design, growth, fabrication ... |
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| The Impact of Low Temperature Materials on the Breakdown and Noise Properties of GaAs and InP Based Hemt's and FET's |
30 APR 94 |
50 pages |
| Authors:
Umesh K. Mishra; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| The breakdown voltage in GaAs field effect transistors (FET) has been the fundamental limitation of power performance in these devices. Previous studies have identified the high electric field at the drain edge of the gate metal as the cause of breakdown. At the start of this project, we successfully demonstrated that a low-temperature-grown GaAs (LTG-GaAs) surface 'insulator' dramatically improved the breakdown voltage in a GaAs MISFET. Subsequent device studies have ... |
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Reports by Author
