| 摘要 |
PURPOSE:To enhance a pinch-off characteristic and to realize a high-speed operation by installing a buffer layer which has an active layer composed of InGaAs and is composed of a superlattice where InAlAs and InAlGaAs are laminated alternately so that the generation of, a two-dimensional electron gas on the side of the buffer layer in an active layer can be suppressed. CONSTITUTION:A high electron-mobility transistor is constituted by a semiinsulating InP substrate 11, an InAlAs/InAlGaAs superlattice (a buffer layer) 12, an undoped InGaAs layer (a channel layer; an active layer) 13, an n-InAlGaAs layer (an electron supply layer) 14, an n-InGaAs layer (a contact layer) 15, a gate electrode 16, a source electrode 17 and a drain electrode 18. If the superlattice as the buffer layer 12 is constituted by InAlAs and InAlGaAs in this manner, an InAlGaAs (quaternary) conduction band is at a high level; a difference between the conduction band of InAlAs and that of InAlGaAs becomes small; it becomes difficult for a donor in a deep impurity level of InAlAs to move beyond InAlGaAs. Accordingly, it is possible to suppress the generation of a two-dimensional electron gas on the side of the buffer layer 12 of a hetero interface. |
