Normally‐Off Operation of Lateral Field‐Effect Transistors Fabricated from Ultrapure GaN/AlGaN Heterostructures

The presence of a 2D electron gas (2DEG) in GaN/AlxGa1–xN heterostructures with low aluminum mole fraction is found to depend on the residual background impurity concentration in the GaN/AlGaN layer stack. At a residual donor level of 2 × 1016 cm−3, a 2DEG is absent at 300 K in dark environment. Such a 2DEG can be generated at the GaN/AlGaN interface either by illumination with ultraviolet light or by applying an electrostatic potential. The latter results in inherently normally‐off switching characteristics of lateral field‐effect transistors. A 2D electron gas (2DEG) is found to be absent at 300 K and in the dark in ultrapure GaN/AlGaN heterostructures grown by molecular beam epitaxy. However, such a 2DEG can be generated electrostatically and under ultraviolet (UV) illumination at a GaN/AlGaN interface. This characteristic results in inherent normally‐off operation of lateral field‐effect transistors in dark environment.