Comprehensive study of a Pd-GaAs high electron mobility transistor (HEMT)-based hydrogen sensor

Ching Wen Hung, Han Lien Lin, Huey Ing Chen, Yan Ying Tsai, Po Hsien Lai, Ssu I. Fu, Hung Ming Chuang, Wen Chau Liu

Research output: Contribution to journalReview articlepeer-review

29 Citations (Scopus)


An interesting Pd-GaAs high electron mobility transistor (HEMT) hydrogen sensor is fabricated and studied. For the studied device, a 5 nm-thick undoped GaAs cap layer is grown to suppress the oxidation of the underneath Al0.24Ga0.76As layer. Comprehensive analysis on the electrical properties including equilibrium adsorption (steady-state) and kinetic adsorption (transient) is presented. Experimentally, a high current variation of 17.1 mA/mm is obtained in 9970 ppm H2/air gas at 323 K. A high channel conductance variation of 25.1 mS/mm is also found under the same conditions. This indicates that, in hydrogen-containing ambience, the channel resistance reduces in the linear region of transistor operation. The reaction enthalpy and entropy are -112.74 kJ mol-1 and -367.39 J mol-1 K-1, respectively. This interprets that the hydrogen adsorption process is exothermic and the hydrogen atoms are more ordered when they are adsorbed in a dipolar layer at the metal-semiconductor interface. In the transient analysis, the rate constants of the studied device can be calculated. Then the activation energy of about 33.09 kJ mol-1 is obtained.

Original languageEnglish
Pages (from-to)81-88
Number of pages8
JournalSensors and Actuators, B: Chemical
Issue number1
Publication statusPublished - 2007 Mar 8

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry


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