The disclosed technology generally relates to a sensor and methods for making and using the same, and more particularly relates to a sensor configured to sense the presence of at least one fluidum. In one aspect, a sensor for sensing a fluidum in a space adjoining the sensor comprises a two-dimensional electron gas (2DEG) layer stack. The sensor additionally comprises a gate lying adjacent to at least part of the 2DEG layer stack and configured to electrostatically control the electron density of a two-dimensional electron gas (2DEG) in the 2DEG layer stack. The sensor further comprises a source electrode contacting the 2DEG layer stack for electrically contacting the 2DEG. The 2DEG layer stack of the sensor comprises a contact surface contacting the space and provided to contact molecules of the fluidum which is desired to be detected, and the gate of the sensor comprises a doped semiconductor bottom layer of the 2DEG layer stack in electrical contact with at least one gate electrode, where the doped semiconductor bottom layer being located at a side of the 2DEG layer stack opposing the contact surface.