National Cheng-Kung University

National Science Council

Huey-Ing Chen

Wen-Chau Liu

Chung-Fu Chang

Tsung-Han Tsai

Kun-Wei Lin

Shiou-Ying Cheng

Hsi-Jen Pan

Chin-Yi Chu

Tai-You Chen

Yen-I Chou

Chi-Hsiang Hsu

Chun-Tsen Lu

The present invention is a multi-gas sensor and a method for fabricating the multi-gas sensor. The multi-gas sensor comprises a substrate, an epitaxial layer, a metal oxide layer, a first metal layer, a second metal layer and multiple third metal layers. The method for fabricating the multi-gas sensor comprises steps of forming an epitaxial layer on a substrate; etching the epitaxial layer to form a first epitaxial structure and a second epitaxial structure a fixed distance from the first epitaxial structure; forming a metal oxide layer on the first epitaxial structure; forming a first metal layer that has at least two metal layers on the second epitaxial structure; forming a second metal layer a fixed distance from the first metal layer on the second epitaxial structure; forming third metal layers respectively on the metal oxide layer, the first metal layer and the second metal layer.

Multi-gas sensor and method of fabricating the sensor

A semiconductor diode with hydrogen detection capability includes a semiconductor substrate, a doped semiconductor active layer formed on the substrate and made from a compound having the formula XYZ, in which X is a Group III element, Y is another Group III element different from X, and Z is a Group V element, a semiconductor contact-enhancing layer formed on the active layer and made from a compound having the formula MN, in which M is a Group III element, and N is a Group V element, an ohmic contact layer formed on the semiconductor contact-enhancing layer, and a Schottky barrier contact layer formed on the active layer. The Schottky barrier contact layer is made from a metal that is capable of dissociating a hydrogen molecule into hydrogen atoms.

Semiconductor diode capable of detecting hydrogen at high temperatures

A high-sensitivity Pd/InP hydrogen sensor was made by a) forming an n-type or p-type semiconductor film on a semiconductor substrate; b) forming a patterned first metal electrode on the semiconductor film, wherein the first metal electrode forms an Ohmic contact with the semiconductor film; and c) forming a second metal electrode on the semiconductor film, the second metal electrode being isolated from the first metal electrode, wherein the second metal electrode forms a Schottky contact with the semiconductor film, wherein a thickness of the second metal electrode and a material of which the second metal electrode is made enable a Schottky barrier height of the Schottky contact to decrease when hydrogen contacts the second metal electrode. The second metal electrode can be physical vapor deposited or electroless plated.

Process for preparing a hydrogen sensor

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.

Hydrogen-sensitive palladium (PD) membrane/semiconductor schottky diode

Growing community of inventors

Tainan, Taiwan

Huey-Ing Chen