GaAs diodes as broad spectrum biochemical sensors

Transport measurements such as IV curves and differential conductance demonstrate the capability of GaAs based PIN diodes to act as a detector of various ions and biochemically relevant molecules. These ions and molecules are in an electrolyte solution in contact with the outer GaAs surface. We show spectroscopic data demonstrating varied probabilities that the bonds Ga-H, Ga-O, As-H, and As-O are created at the interface, and we also correlate spectroscopic data with transport data leading to a partial correlation between the two types of data. Additionally, we quantified how surface conductivity depends on the partial charge. The capacitance-voltage measurements are then used to quantify changes in Debye length, pointing towards the need to have an atomistic level model of Helmholtz layers and Debye length. Lastly, we demonstrate how such devices could be used as sensors by estimating their sensitivity levels. As an example of application for biochemical sensing, we show how various amino acids can be detected with the same microdevice.