Air-stable, aluminium oxide encapsulated graphene phototransistors

Graphene has garnered significant interest in optoelectronics due to its unique properties, including broad wavelength absorption and high mobility. However, its weak stability in ambient conditions requires encapsulation for practical applications. In this study, we investigate graphene CVD-grown field-effect transistors fabricated on Si/SiO₂wafers, encapsulated with aluminum oxide (Al₂O₃) of different thicknesses. We measure and analyze their optoelectronic response across wavelengths from near-ultraviolet to near-infrared. We find that, while having a negligible role in the photogating process, the Al₂O₃layer leads to stable and reproducible transferring curves operating in ambient conditions for over a month, with stable responsivities up to 1.5 A/W at the shortest wavelength. Moreover, the transferring curves are stable at elevated temperatures up to 107 °C. We also show that the sample performance can be tuned by changing the thickness of the Si/SiO₂and Al₂O₃layer which brings further perspectives in developing robust sample technologies, especially in the ultraviolet region where the responsivity increases. Aluminum oxide encapsulated graphene-based photodetectors can thus be interesting for applications in air and at elevated temperatures.