ICMCTF2003 Session H2-1: Thin Films and Processes for Next Generation Devices

Thursday, May 1, 2003 8:30 AM in Room San Diego
Thursday Morning

Time Period ThM Sessions | Abstract Timeline | Topic H Sessions | Time Periods | Topics | ICMCTF2003 Schedule

Start Invited? Item
8:30 AM Invited H2-1-1 High Speed, Low Power Sb-Based Transistors
J.B. Boos, R. Magno, B.R. Bennett, K. Ikossi, M.G. Ancona, W. Kruppa, D. Park, M.J. Yang, K.D. Hobart, J. Mittereder, W. Chang, R. Bass, E.R. Glaser, N.A. Papanicolaou, B.V. Shanabrook, H.B. Dietrich (US Naval Research Laboratory); R. Tsai, M. Barsky (TRW Space and Electronics Group); S.E. Mohney, S. Wang (Penn State University); N.H. Turner (The George Washington University)

Future high-speed receiver and logic applications that require lightweight power supplies, long battery lifetimes, improved efficiency, or high component density will require transistors that consume less power. Military and commercial applications that would significantly benefit from reduced power consumption include space-based communications, imaging, sensing, high data rate transmission, microair-vehicles, wireless applications and other portable systems. The use of Sb-based transistors in lownoise high-frequency amplifiers, digital circuits, and mixed-signal circuits will provide the enabling technology needed to address these rapidly expanding needs.

AlSb/InAs HEMTs have intrinsic advantages for some of these high-speed, low-power-consumption applications due to the attractive material properties of this heterojunction material system that include high values of mobility, channel conductivity, and peak electron velocity at low electric field. Intrinsic fT values of 250 GHz have been obtained at VDS = 600 mV and an fT of 90 GHz has been measured at VDS = 100 mV1. HEMTs with a TiW/Au gate metallization and a reduced 50Å spacer layer above the channel exhibit a maximum transconductance at VDS = 550 mV of 1.4 S/mm. HEMTs with the addition of a stable AlGaSb buffer layer were also recently fabricated and characterized2. The AlGaSb insert enables a shallow mesa isolation etch and provides a method of device formation that is completely compatible with existing space-flight qualified production MMIC processes.

Heterojunction bipolar transistors using InzGa1-zSb for the base and InxAl1-xAsySb1-y alloys for the collector and emitter are also being explored. The InGaSb base is attractive due to its narrow bandgap, its good hole transport characteristics, and its ease in forming low-resistance ohmic contacts. Equally important is the fact that the InGaSb base can be used with a collector and an emitter made from a variety of InAlAsSb alloys enabling a wide range of heterojunction design flexibility. Modeling of the DC current-voltage characteristics indicate that current gain in excess of 500 may be obtained. Good diode characteristics with an ideality factor of 1.1 have recently been obtained for InAlAsSb p-n junctions grown at a lattice constant of 6.2Å using Te for the n-type dopant and Be for the p-type dopant3. Lowresistance Pd/W/Au ohmic contacts to the p-InGaSb base material which are shallow and thermally stable have also recently been demonstrated4. In this talk, the current status of the design, fabrication, and characterization of Sb-based HEMTs (6.05 Å) and HBTs (6.2 Å) in our group will be presented including emphasis on the Schottky and ohmic contact methodologies employed to achieve shallow contacts and improved thermal stability.

1 J. B. Boos et al., J. Vac. Sci. Technol. B, 17 (3), 1022-1027, (1999).

2 R. Tsai et al., Proc. of the 2002 Lester Eastman Conference on High Performance Devices

3 R. Magno et al., Proc. of the 2002 Lester Eastman Conference on High Performance Devices

4 S. H. Wang et al., submitted for publication in J. Vac. Sci. Technol. This work was supported by the Defense Advanced Research Projects Agency and the Office of Naval Research.

9:10 AM Invited H2-1-3 Passivation of Type II (InAs/GaSb) Superlattices for VLWIR FPA Applications
M. Razeghi (Northwestern University)
Throughout the past few years, excellent detectors have been demonstrated in the area of Type II InAs/GaSb superlattices, which covers a very wide range of infrared spectrum from 2 µm up to 32 µm at least. As a progress towards commercialization and focal plane array applications for Type II InAs/GaSb superlattice detectors, passivation becomes an important issue. We will present the most current progress towards successful passivation on Type II InAs/GaSb superlattice detectors. Detector performance before and after passivation will be covered in this talk.
9:50 AM Invited H2-1-5 Ferromagnetism in GaN and SiC Doped with Transition Metals
S.J. Pearton (University of Florida); Y.D. Park (Seoul National University, South Korea); C.R. Abernathy, M.E. Overberg, G.T. Thaler, J. Kim, F. Ren (University of Florida); J.M. Zavada (US Army Research Office); R.G. Wilson (Consultant)
Existing semiconductor electronic and photonic devices utilize the charge on electrons and holes in order to perform their specific functionality such as signal processing or light emission. The field of semiconductor spintronics seeks to exploit the spin of charge carriers in new generations of transistors, lasers and integrated magnetic sensors. The utility of such devices depends on the availability of materials with practical magnetic ordering temperatures. Here we summarize recent progress in the development of GaN, SiC and other wide bandgap semiconductors which retain ferromagnetic properties above room temperature.
10:30 AM Invited H2-1-7 What's New in Ohmic Contacts to Compound Semiconductors
J. Woodall (Yale University)

As devices become scaled to ever smaller dimensions, parasitic components of larger versions of devices start to not only become important to performance but can actually dominate performance especially at high current densities. Of the many parasitic components, none is more intriguing and perplexing than excessive ohmic contact resistance. A major reason for this is there is no agreed-on theory that adequately explains the electronic behavior at metal/semiconductor interfaces.

Therefore, the technical community has had to rely on "empirical engineering" to develop suitable enabling contact technologies. This talk will review the current status of ohmic contact technology for commercially important compound semiconductors and present new enablers that yield adequate contact resistances.

11:10 AM H2-1-9 Effect of Deposition Parameters on the Microstructural Evolution and Electrical Properties of Charge-balanced Barium Strontium Titanate Ferroelectric Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition
C.F. Fountzoulas, D.M. Potrepka, S.C. Tidrow (Army Research Laboratory)

Thin films, from novel B-site substituted barium strontium titanate (BSTO) bulk targets, have been deposited using the pulsed laser deposition (PLD) technique. The measured electrical properties of these thin films will be compared with the electrical properties of the bulk materials. In these materials, an applied electric-field can be used to change the dielectric constant of the material, hence, the capacitance or phase velocity in RF/microwave devices can be tuned in real time for a particular application. The microstructure of the film influences the electronic properties which in turn influence the performance of the film.

Selected charge-balanced binary substitutions, using A3+ = Y3+ and Sc3+ and A5+ = Ta5+ were made for Ti+4 to obtain Ba0.60√sub 0.40Sc0.05Ta0.05Ti0.90O3 and Ba0.60√sub 0.40Y0.05Ta0.05Ti0.90O3 targets. Thin films were synthesized on MgO (100) substrates, at substrate temperatures ranging from 4000C to 6000C and oxygen partial pressure ranging from 30 to 50 mTorr, at 500 mJ laser energy and 10 pulses per second using the pulsed laser deposition technique. The thickness of the thin films varied from 1.5 to 3.0 µm. Shallow glazing angle x-ray diffraction (GAXRD) studies of the synthesized thin films have revealed a preferred orientation. The effect of the ionic substitution and substrate temperature in conjunction with the effect of the oxygen partial pressure on the microstructure, and mechanical and electrical properties of the thin films were studied using x-ray diffraction, SEM, AFM, Rutherford backscattering, nanoindentation and capacitance measurements and will be discussed in detail.

11:30 AM H2-1-10 Structural and Dielectric Properties of Heterostructured BST Thin Films by Sol-Gel Technique
M. Jain, S.B. Majumder, R.S. Katiyar (University of Puerto Rico)
Fabrication of high quality Bax√sub 1-xTiO3 films exhibiting large tuning of the dielectric constant by applied electric field and low loss tangent (tanδ) values, is an important technological issue for high frequency applications. The maximum tunability {(C0-Cv)/C0} with low dielectric losses are normally observed in the paraelectric phase close to the transition temperature. Therefore, the figure of merit (defined by K=tunability/tanδ) should peak around the room temperature for Bax√sub 1-xTiO3 with x = 0.4 to 0.6. Recently we have prepared heterostructured Ba0.5√sub 0.5TiO3 {BST(50/50)} thin films with intermediate low loss MgO layers and showed the imrovement in the figure of merit (64°/dB for the heterostructure film as compared to 29°/dB of pure BST (50/50) tihn film) for high frequency phase shifter. We have also prepared MgTiO3:BST heterostructured thin films. The structural, microstructural, dielectric, and electrical properties of the films including phase shifter measurements made on these films will be discussed.
11:50 AM H2-1-11 The Influence of PH Value on the Growth Morphology of (Ba, Sr)TiO3 Thin Films Prepared by Sol-Gel Technique
S. Agarwal, G.L. Sharma (Indian Institute of Technology Delhi, India)
Polycrystalline (Ba, Sr)TiO3 (BST) thin films are prepared by sol-gel technique using titanium isopropoxide and 2-ethyl hexanoate precursors for barium and strontium. The pH value of precursor sol was adjusted by adding ammonium hydroxide. These films are studied at 7.4 & 9.0 pH and at different molarities ranging from 0.15 M to 0. 30 M. The X-ray diffractometry (XRD) pattern clearly shows a preferential orientation of crystallites in (110) direction with increase of pH. These films are porous and adsorb water vapor when exposed to humid environment. Atomic force microscopy (AFM) show that grain size decreases from 67 to 38 nm with the increase of pH from 7.4 to 9.5 respectively, while surface roughness decreases from 0.81 to 0.74 nm. We have found that sensitivity, linearity and response time of the humidity sensor utilizing these films can be improved by tailoring the process parameters such as pH and molarity of the precursor sol. The sensitivity is found to be maximum at 0.30 M. It is calculated to be 46 at 0.30 M, which is higher as compared to the values 40 and 15 at 0.15 M and 0.20 respectively for a given 7.4 pH of sol. As we increase the pH of sol it was observed that sensitivity of the deposited films increases and reaches to the maximum value (~ 189) at 9.0 pH.
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