Pressure-induced changes in the conductivity of AlGaN∕GaN high-electron mobility-transistor membranes

$\mathrm{AlGaN}∕\mathrm{GaN}$ high-electron-mobility transistors (HEMTs) show a strong dependence of source∕drain current on the piezoelectric-polarization-induced two-dimensional electron gas. The spontaneous and piezoelectric-polarization-induced surface and interface charges can be used to develop very sensitive but robust sensors for the detection of pressure changes. The changes in the conductance of the channel of a $\mathrm{AlGaN}∕\mathrm{GaN}$ high electron mobility transistor (HEMT) membrane structure fabricated on a $\mathrm{Si}$ substrate were measured during the application of both tensile and compressive strain through changes in the ambient pressure. The conductivity of the channel shows a linear change of $-(+)6.4\times {10}^{-2}\mathrm{mS}∕\mathrm{bar}$ for application of compressive (tensile) strain. The $\mathrm{AlGaN}∕\mathrm{GaN}$ HEMT membrane-based sensors appear to be promising for pressure sensing applications.