Abstract：The characteristics of AlGaN/GaN Schottky diodes as polar liquid sensors are reported. Circular structures, with a gate metal diameter of 200 μm , are designed and fabricated by using a optical lithography process. Ni/Au and Ti/Al/Ni/Au metals are used as the Schottky contact and the ohmic contact, respectively. The Schottky diodes exhibit large changes in reverse leakage current at a bias of ?20 V in response to the surface exposed to various polar liquids, such as acetone and ethanol. The effective Schottky barrier height of the diodes is also changed with the polar liquids. The polar nature of the liquids leads to a change of surface charges, producing a change in surface potential at the semiconductor/liquid interface. The effect of the SiNx passivation layer thickness on the liquid sensing is also discussed. The results demonstrate that the AlGaN/GaN heterostructures are promising for polar liquids, combustion gas, biological, and strain sensing applications.
2013, Vol. 30 
