Detection of Amino Acids and Other Biochemical Molecules with GaAs Schottky Diodes

The sensitivity of the GaAs surface makes it a good candidate for sensing various molecular species of interest in biochemistry. Simultaneously, the growth in nanofluidics applications calls for detailed understanding of liquid-solid interfaces for a variety of interfaces’ combinations. The 1V operation range for GaAs Schottky sensor is shown to be sufficient to detect H₂O, D₂O, -OH, as well as PBS solutions of various concentrations at 300K. We show how interfacial density of states changes with each compound probed, and how this density changes with the applied electric field. Inorganic bonds, such as Ga-H, Ga-O (and related As-based ones), are differentiated through correlation of transport and FTIR data of liquid-solid interfaced. The same GaAs Schottky diode can be used to distinguish between different types of amino acids (non-polar, polar, and basic) through the specific examples of Gly, His, and Cys, respectively. Finally, the built-in potential and the interfacial density of states are determined as a function of the pH factor of solutions tested (4 < pH < 9). These results offer perspective on developing GaAs based system for micro- and nanofluidics based detection and differentiation of peptides.