Regensburg 2004 – scientific programme
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HL: Halbleiterphysik
HL 16: GaN: Bauelemente
HL 16.1: Talk
Tuesday, March 9, 2004, 10:15–10:30, H13
Pt/GaN Schottky Diodes for Hydrogen Gas Sensors — •M. Ali1, V. Cimalla1, V. Tilak2, D. Merfeld2, P. Sandvik2 und O. Ambacher1 — 1Technical University Ilmenau, Center of Micro- and Nanotechnologies, Gustav-Kirchhoff-Str. 1, D-98693 Ilmenau, Germany — 2General Electrics, General Electrics Global Research Europe, Wehrle Strasse 13, D-81675 München, Germany
The performance of Pt/GaN Schottky diodes with different thickness of the catalytic metal were investigated as hydrogen gas detectors. The sensors were fabricated based on epitaxial Si-doped Ga-face GaN layer (ND = 9 × 1016 cm−3) grown up to a thickness of about 3 µ m by metalorganic chemical vapour deposition on c-plane sapphire substrates. The area as well as the thickness of the Pt were varied between 250 µ m2 and 1000 µ m2, 80 and 400 Å, respectively. The Pt-Schottky-diodes exhibited at room temperature ideality factors, saturation currents and barrier heights between 1.3 and 3.3, 6× 10−11 and 1.25 × 10−7 A and 0.64 and 0.99 eV, respectively. The sensitivity to hydrogen gas was investigated in dependence on active area, Pt thickness and the operating temperature for 1% hydrogen in synthetic air. The change in gate voltage of the diode at a fixed current was monitored as the diode was exposed to hydrogen gas and for comparison to dry air in order to determine the sensor sensitivity. We observed a significant increase of sensitivity and decrease of response time by increasing the temperature of operation to about 350∘C and by decreasing the Pt thickness down to 80 Å.