WJ Communications Research Scientist to Present at 19th Reliability of Compound Semiconductors Workshop -- ROCS-2004 -- Conducted by JEDEC, EIA & IEEE- Electron Devices Society.

SAN JOSE, Calif. -- WJ Communications, Inc. (Nasdaq:WJCI), a leading designer and supplier of high-performance RF semiconductors and multi-chip modules (MCM), today announced that Mr. Satbir Madra, Senior Research Scientist at WJ, will present a research paper at the 19th Workshop on Reliability of Compound Semiconductors, (formerly, GaAs Reliability Workshop) to be held at Monterey, California on October 24, 2004. This premier event is sponsored by JEDEC-JC14.7 Committee, under co-sponsorship with the Electron Devices Society (EDS) of the IEEE. The event is held jointly under the auspices of both, academia, - California Institute of Technology (CIT), University of Parma, Italy, Jet Propulsion and Naval Research Laboratories, and several key technology companies. The conference will address the latest developments in research and technology relating to reliability of III-V semiconductors including Gallium-Nitride and Gallium-Arsenide applications.

The topic of Mr. Madra's presentation will be, "Reliability Characterization of MOVPE grown n-GaInP/p-GaAs Heterojunctions vis-a-vis High Temperature Operation through Photoreflectance Spectroscopy (PRS), Transmission Electron Microscopy and Deep Level Transient Spectroscopy (DLTS)."

Mr. Satbir Madra said, "Metalorganic Vapor Phase Epitaxy (MOVPE) was used to grow lattice-matched n-GaInP/p+GaAs heterojunctions and full Heterojunction Bipolar Transistor (HBT) cells on GaAs wafers. The GaInP/GaAs heterojunctions, which constitute the emitter-base junction for contemporary Heterojunction Bipolar Transistors, were analyzed for degradation under high temperature and current stress. n+GaInP/p+GaAs tunnel diodes were fabricated for carbon kinetics. Using DLTS, fabricated GaInP/GaAs diodes were characterized for recombination trap kinetics and trap cross-sections. Succinctly, models for degradation mechanisms through REID and REDR are presented."

Paper Synopsis

1. Photoreflectance (PR) Spectroscopy was used to characterize the evolution of the GaInP bandgap energy, and also to determine the degree of disorder (n) in the GaInP epitaxial material. The GaInP bandgap has been characterized just after i) GaInP deposition, ii) after emitter n-GaAs and n-InGaAs cap development, and iii) after high temperature excursion cycles. The CuPt-type ordering leading to valence band splitting (VBS) and degradation of the optical properties of the heterojunction were analyzed. We use 'Levenberg-Marquardt' algorithm for PR line-shape fitting. Bandgap evolution was traced for the departure from initial state due to effects from 'pseudomorphic' strain, elevated temperature and current stress effects.

2. Additionally, n+GaInP/p+GaAs tunnel diodes have been developed using Molecular Beam Epitaxy (MBE) in order to determine the behavior of carbon dopant in GaAs under high-density minority-carrier injection. Carbon diffusion kinetics, and activation energy for diffusion has been determined. We propose a 'Recombination-Enhanced-Impurity-Diffusion' (REID) mechanism for carbon clustering effects, involving the kick-out reaction followed by the dissociation of the split-interstitial (CC)(100) complex into substitutional and interstitial C atoms with lower activation energies, leading to carbon precipitation. We observe carbon clusters through TEM.

3. Deep Level Transient Spectroscopy (DLTS) was used for determining existence of recombination traps, trap kinetics and trap cross-sections. We examine the role of traps and dangling bonds. Diodes were generated using the GaInP/GaAs heterojunctions. A series of wet etch processes were used to isolate the base mesas and annealed ohmic contacts were established. The emitter contact area was 75 x 75 microns, while the base contact area was slightly larger. Using deep level transient spectroscopy (DLTS), and applying different reverse bias voltage levels, and filling pulse heights, an attempt was made to identify trap signals in the different depth regions. We correlate the DLTS results to propose the 'Recombination Enhanced Defect Reaction, (REDR) effects. The role of dangling bonds and antisite effects (anion-on-cation site) is also discussed.

4. Finally, High Resolution Transmission Electron Microscopy (HRTEM) has been used to trace the evolution of the heterojunction. We observe distinct lattice strain effects from high temperature and current stresses. Misfit dislocations are absent. No spinodal composition modulation effects were observed. Spinodal effects can reduce the critical thickness for introduction of misfit dislocations in the GaInP epilayer.

Mr. Robert Bayruns, Vice President of Engineering at WJ said, "Satbir's work highlights WJ's keen commitment to semiconductor product quality and reliability. In-depth characterization and detailed understanding of semiconductor products is essential for optimal performance and long-term reliability, particularly for products involving compound semiconductor technology. This work investigates and provides great understanding about the degradation mechanisms in GaInP/GaAs heterointerfaces involved in today's state-of-the-art HBT designs."

Author Profile: Mr. Satbir Madra is a Senior Research Scientist at WJ Communications. He is member of the IEEE, of the Materials Research Society (MRS), and of the International Microelectronics and Packaging Society (IMAPS). He is a honorary member of Pi Tau Sigma. He has extensive experience in the area of semiconductor manufacturing and solid state physics applications. He received his bachelor and graduate degrees in mechanical engineering with a special focus on VLSI fabrication. Some of his interests lie in the areas of gettering of silicon, development of low-k IMD films, CVD and High Density Plasma Deposition, X-ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Fourier Transform Infrared Microscopy (FTIR). His interests also lie in the areas of disk drive mechanics, thermal characterization, numerical analyses, carrier transport, device physics, and analytical modeling.

About ROCS 2004

ROCS 2004 (http://jedec.org/Home/gaas/default.cfm), is the premier conference on reliability of compound semiconductors, sponsored jointly by the JEDEC Committee, JC-14.7 on Gallium-Arsenide Reliability and Quality Standards, The Electron Devices Society (EDS) of the Institute of Electrical and Electronic Engineers (IEEE) (http://ieee.org), and the Electronics Industries Alliance (EIA) (http://www.eia.org). The workshop will be held on October 24, 2004 at The Double Tree Hotel in Monterey, California, USA. Dr. Anthony A. Immorlica of BAE Systems shall be the General Chair for this event.

About WJ Communications

WJ Communications Inc. is a leading RF semiconductor company focusing on the design and manufacture of high-quality devices, chip sets and multi-chip modules (MCMs) for telecommunications, RF identification (RFID) and homeland security systems worldwide. WJ's highly reliable amplifiers, mixers, RF integrated circuits (RFICs), RFID reader modules, chipsets and MCM products are used to transmit, receive and process signals that enable current and next generation wireless and wireline services. For more information visit www.wj.com or call [phone].

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