InAS-based NOx gas sensor
A van der Pauw (VDP) sensor comprising an electronic circuit electrically coupled to a surface, the surface comprising a type IIIV material, and the electronic circuit measuring a sheet resistivity of the surface using a VDP technique. The VDP sensor may further comprise a macromolecule, such as a porphyrin, an oligonucleotide, a protein, a polymer, or a combination thereof in contact with the surface. The VDP sensors may be arranged in an array of similar or different sensors. An electronic circuit electrically coupled to a type III-V material having a two-dimensional electron gas, such as InAs or InN, the electronic circuit measuring an electrical property of the type III-V material having a two-dimensional electron gas.