Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Responsive to non-optical – non-electrical signal
Patent
1999-05-28
2000-12-12
Mintel, William
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Responsive to non-optical, non-electrical signal
257253, 257414, 257472, 257473, 257485, 438 49, 204431, H01L 2358
Patent
active
061602787
ABSTRACT:
In this invention, a new, simple and small-size hydrogen-sensitive palladium (Pd) membrane/semiconductor Schottky diode sensor has been developed and fabricated. First, a high quality undoped GaAs buffer layer and an n-type GaAs epitaxial layer with the carrier concentration of 2.times.10.sup.17 cm.sup.31 3 is grown by molecular beam epitaxy (MBE) on a semi-insulated GaAs substrate. Then a thin Pd membrane is evaporated on the surface of the n-type GaAs epitaxial layer by the vacuum evaporation technique. It is well-known that palladium metal has excellent selectivity and sensitivity on hydrogen gas. When hydrogen gas diffuses to the Pd membrane surface, the hydrogen molecules will dissociate into hydrogen atoms. Some of the hydrogen atoms diffuse through the thin metal layer and form the palladium hydride near the metal-semiconductor interface. The hydride may effectively lower the work function of Pd metal. The lowering of work function results in the reduction of Schottky barrier height at the Pd metal-GaAs semiconductor interface and the modification in the measured current-voltage characteristics of the studied device. Experimental results reveal that, during the hydride formation process, the forward- and reverse-biased currents are increased by the increase of hydrogen concentration. It also demonstrates that the Schottky barrier height is indeed decreased with increasing the hydrogen concentration. Therefore, the studied device can be used in fabricating a high-performance hydrogen-sensitive sensor.
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Chen Huey-Ing
Cheng Shiou-Ying
Liu Wen-Chau
Mintel William
National Science Council
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