| 摘要 |
A group-III nitride-based field-effect transistor exhibiting an improved breakdown voltage achieved by reducing the leak current component caused by conduction by residual carriers in the buffer layer, producing an improved channel electron confinement (carrier confinement) effect, and having an enhanced pinchoff characteristic (to suppress the short-channel effect). When the invention is applied to a GaN-based field-effect transistor, separately from GaN in the channel layer, a modulated-composition (gradient-composition) AlGaN layer is used as a buffer layer, which has a region where the Al composition is gradually decreased from the bottom surface to the top surface but partially increased in an intermediate part. The sum a of the thicknesses of the electron supply layer and the channel layer is determined so as to satisfy the relation Lg/a = 5 where Lg is the gate length of the fabricated FET, and the thickness of the channel layer is determined to be 5 or less times the de Broglie wavelength at room temperatures of the two-dimensional electron gas accumulated in the channel layer (about 500 Å). |
