Interdigitated Electrode Design Research Articles

Optimization of electrode configuration in large GaInN light‐emitting diodes

AbstractFlip‐chip 1×1 mm2 GaInN‐based light‐emitting diodes (LEDs) with an interdigitated electrode design were investigated. Two types of GaInN‐based LED having a 4‐line p‐electrode with a width of 160 μm and an 8‐line p‐electrode with a width of 50 μm were fabricated. The 8‐line device with a 50‐μm‐wide p‐electrode shows 20% higher output power at a forward current of 350 mA than the 4‐line device with a 160‐μm‐wide p‐electrode. The three dimensional simulation of the LED operation was conducted to clarify the origin of the difference in output power. From simulation results, the output power of the device with a 50‐μm‐wide 8‐line p‐electrode was estimated to be 10% higher than that of the device with a 160‐μm‐wide 4‐line p‐electrode. A large difference in current density between the middle and edge of each 160‐μm‐wide electrode is suggested. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High-frequency monolithic thin-film piezoelectric-on-substrate filters

A class of micromachined acoustic filters is presented in which the number of individual resonant structures is reduced to 1 (monolithic filter). This resonant structure is comprised of a stack of thin-film piezoelectric-on-silicon. Symmetric and anti-symmetric resonance modes (dual modes) of the silicon structure are piezoelectrically excited and coupled to realize a 2-pole narrowband filter. High-order lateral bulk acoustic resonance modes of a rectangular plate are utilized to design dispersed-frequency UHF filters fabricated on a single substrate. Thickness mode filters are also realized at GHz frequencies using a new interdigitated electrode design. Additionally, it is shown that the filter bandwidth can be controlled by changing the dimensions of the resonant structure and the electrode pattern. Narrowband lateral mode filters with filter Q’s larger than 300 at ~440 MHz and thickness mode filters with filter Q’s in the range of 150–900 at ~3.1 GHz are demonstrated.

Glass-based BioMEMS devices for optically excited cell impedance measurement

This paper presents for the first time the design and fabrication of BioMEMS devices for living cells’ electrochemical impedance measurement under optical excitation. An interdigitated electrode design is adopted in order to increase the sensitivity of living cells’ impedance measurement. The magnitudes of the parasitic components were calculated and their influence on the chip performance was simulated. It is shown that our glass-based realization enables a very good performance up to a measurement frequency of 10 MHz when the solution resistance is 1 MΩ. The main difficulties that had to be solved in the fabrication process were related to adhesion and patterning of the various metal films, and especially to developing the correct bonding recipe. Unlike most of the reported data, no direct bonding was employed in the realization of our devices, but rather an intermediary polymer layer (e.g. SU8 or BCB) was used. The impedance of the devices with living yeast cells are measured with and without laser excitation at 532 nm. The laser excitation also redistributes the cells, and the suspending cells in the PBS buffer settle down much quicker after the light excitation.

Polycrystalline diamond photoconductive device with high UV-visible discrimination

Planar metal–diamond–metal photoconductive devices have been fabricated from free standing large grain (20–30 μm) polycrystalline thin film diamond. An interdigitated electrode design with spacings of 20 μm was used to produce effective UV photodetecting devices at bias values in the range 0.1–10 V. A methane-air treatment has been used to modify the structures such that unprecedented performance characteristics have been recorded (106 higher response to 200 nm than visible wavelengths, <0.1 nA dark currents); spectral features similar to those observed in natural diamond crystals have been observed indicating that the treatment used led to near ideal electronic characteristics from polycrystalline material.