Electrical characterization of electrolyte/β- Ga₂O₃ junction for biosensing applications

Electrolyte/semiconductor junctions have attracted considerable attention from different disciplines such as physical chemistry and electrochemistry in recent years. Here, we investigated a single-crystal gallium oxide (β-Ga₂O₃)-based electrolyte/semiconductor junction behaving similar to a Schottky type diode, determined its electrical properties and analyzed the junction characteristics under certain conditions (e.g., ionic strength, temperature, etc.). The junction was formed by adding an electrolyte layer with a specific ionic concentration (150 × 10−³ M) on top an n-type β-Ga₂O₃ substrate and a metal contact to assist I-V measurement. The junction diode exhibited rectifying behavior and good electrical characteristics such as an ideality factor of 1.8, a threshold potential (Vbi) of 0.74 eV and a Schottky barrier height (Ø_B) of 1.05 eV. The threshold voltage of the diode can be tuned by changing the ionic strength in the junction layer and the conductivity can be varied by changing the measurement temperature. The sensitivity of the conductivity of the diode to changes in the electrolyte concentration means that it can be used in various applications. As an application of the semiconductor/electrolyte junction, the selective detection of miRNA (let-7a, let-7f) molecules was demonstrated.