Pd-MIS 소자의 수소가스 검지 특성

Characteristics of Pd-MIS devices on hydrogen gas sensing

Hydrogen gas sensors were fabricated after the form of metal/insulator/semiconductor(MIS) structure on a p-type silicon wafer and a insulating layer (silicon dioxide) thickness was changed from $500{\AA}$ to $5000{\AA}$. Their electrical properties were investigated with the variation of the hydrogen gas concentration at room temperature. At the applied forward bias of lV to both ends of Pd-MIS sensors the current was decreased logarithmically with the increase of hydrogen concentration in air. In the case of a thin $SiO_2$ layered ($500{\AA}$) sensor the current ratio was decreased to 25 % at 1 % of hydrogen concentration in air and 50% for a thick $SiO_2$ layered ($5000{\AA}$) sensor. And the response time of the thick insulating layered sensor to 1% hydrogen containing air was about 50 seconds and regeneration time was 2.5 minutes. When a 0.5mA current was appied to the thick insulating layered sensor the maximun voltage shift was calculated to 0.8V in the case of ${\theta}$ = 1 and the Pd surface coverage of hydrogen was increased logarithmically with hydrogen partial pressure.