The disclosed technology generally relates to sensors comprising a two-dimensional electron gas (2DEG), and more particularly to an AlGaN/GaN 2DEG-based sensor for sensing signals associated with electrocardiograms, and methods of using the same. In one aspect, a sensor comprises a substrate and a GaN/AlGaN hetero-junction structure formed on the substrate and configured to form a two-dimensional electron gas (2DEG) channel within the GaN/AlGaN hetero-junction structure. The sensor additionally comprises Ohmic contacts connected to electrical metallizations and to the 2DEG channel, wherein the GaN/AlGaN hetero-junction structure has a recess formed between the Ohmic contacts. The sensor further comprises a dielectric layer formed on a top surface of the sensor.