Schottky diode-based sensors

In this entry, we focus on the discussion of the platform technology for electrochemical sensors, metal oxide semiconductive (MOS) sensors, and piezoelectric based quartz crystal microbalance (QCM) sensors. There are other types of chemical sensors, such as optical sensors, Schottky diode based sensors, calorimetric sensors, field-effect transistor (FET) based sensors, surface acoustic wave sensors, etc. Information of these specific sensors can be found elsewhere and in current journals on sensor technologies. Because of the increasing importance of microfabricated sensors, a brief discussion of microsensors is also given. 

AIGaN/GaN HEMT Schottky diode-based hydrogen sensor... 

Trinchi A, Galatsis K, Wlodarski W, Li YX (2003) A Pt/GajOj-ZnO/SiC Schottky diode-based hydrocarbon gas sensor. IEEE Sensors J 3 548-553... 

Hunter, G.W., Neudeck, P.G., Chen, L.-Y. (1997). SiC-based Schottky diode gas sensor. 7 Int conf Silicon Carbide, Ill-Nitrides and Related Materials, Stockholm, Sweden, Trans.Tech., Vol.2, pp. 1093-10%... 

The hydrogen sensitivity of palladinm-oxide-semiconductor (Pd-MOS) strnctnres was first reported hy Lnndstrom et al. in 1975 [61]. A variety of devices can he nsed as field-effect chemical sensor devices (Fignre 2.6) and these are introdnced in this section. The simplest electronic devices are capacitors and Schottky diodes. SiC chemical gas sensors based on these devices have been under development for several years. Capacitor devices with a platinum catalytic layer were presented in 1992 [62], and Schottky diodes with palladium gates the same year [63]. In 1999 gas sensors based on FET devices were presented [64, 65]. There are also a few publications where p-n junctions have been tested as gas sensor devices [66, 67]. 

Schottky diode sensors based on other wide bandgap materials have also been investigated, as previously mentioned. GaN Schottky diodes processed on either the Ga or N face have been examined by Schalwig et al. [11,21]. A Pt/GaN Schottky diode with a barrier height of 1-eV has been shown to reversibly transform into an ohmic contact through exposure to [94]. Kokobun et al. have also investigated Pt-GaN Schottky diodes as hydrogen sensors up to 600°C [15]. 

Fig. 1 (a) Schematic diagram of the silicon-based hydrogen sensor. The Pd alloy Schottky diode (rectangular regions) resides symmetrically on either side of a heater and temperature detector, (b) Picture of the packaged sensor [6]... 

Tiinchi A, Woldarski W, Li YX (2004) Hydrogen sensitive Ga O Schottky diode sensor based on SiC. Sens Actuators B 100 94-98... 

Tuyen LIT, Vinh DX, Khoi PH, Gerlach G (2002) Highly sensitive NOx gas sensor based on a Au/n-Si Schottky diode. Sens Actuators B 84 226-230... 

MIS, Schottky diode, and p-n-junction-based gas sensors can also be of capacitance type. The construction and principles of operation of such sensors can be found in the Introduction and review papers (Lundsfiom 1981). 

Potje-Kamloth, K. (2001) Conducting polymer based Schottky and heterojunctions diodes and their sensor application. In Nalwa, H.S. (Ed.) Handbook of Surfaces and Interfaces of Materials, Vol. 5. Academic Press, p. 445—494. 

Potje-Kamloth K (2001) Conducting polymer-based Schottky barrier tmd heterojunction diodes and their sensor application. In Nalwa HS (ed) Handbook of surfaces tmd interfaces of materials, vol 5. Academic, San Diego, CA, pp 445-494... 

---