Effect of bias voltage polarity on hydrogen sensing with AlGaN/GaN Schottky diodes

✍ Scribed by T.J. Anderson; H.T. Wang; B.S. Kang; F. Ren; S.J. Pearton; A. Osinsky; Amir Dabiran; P.P. Chow

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 452 KB
• Volume: 255
• Category: Article
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2008.07.173

✦ Synopsis

Improved methods for hydrogen leak detection are gaining interest as applications emerge in hydrogen-powered automobiles, proton-exchange membrane fuel cells, solid oxide fuel cells for spacecraft, and other industrial long-term sensing applications. Considerable progress has been demonstrated to date on hydrogen sensors based on GaN or SiC [1][2][3][4][5][6][7][8][9][10]. The wide-bandgap nature of these semiconductors offers the ability to operate at much higher temperatures (up to 500 8C), and to integrate them on-chip with power amplifiers and wireless transmission circuits [11]. Specifically, the AlGaN/GaN high electron mobility transistor (HEMT) structure is particularly well suited for this application. The high electron sheet carrier concentration is induced by piezoelectric polarization and spontaneous polarization of the AlGaN-GaN materials and there are positive charges formed on the top of the HEMT structure to balance the induced electrons in the twodimensional electron gas channel (2DEG) at the AlGaN/GaN interface. HEMT structures demonstrate an increased sensitivity relative to Schottky diodes fabricated on GaN layers due to any slight change of the HEMT ambient affecting the positive charges, which will change the 2DEG concentration. Typically the hydrogen sensing mechanism is ascribed to the dissociation of the impinging * Corresponding author.