| 摘要 |
PURPOSE:To increase mutual conductance and to improve FET characteristics such as a noise factor or power gain, by providing a high dopant concentration region at the interface between a buffer layer and an active layer. CONSTITUTION:A buffer layer 6 is constituted by a P<-> type lowconcentration sub-layer 6a and a P<+> type high-concentration sub-layer 6b. A large amount of silicon is absorbed by the P<+> type high-concentration sub-layer 6b. Then an N<-> type active layer 7 is formed and an N<+> type ohmic contact layer 8 is formed on the active layer 7. As a result, a region 10 with a high concentration of dopant is created at the interface between the buffer layer 6 and the active layer 7. This high dopant concentration region 10 is used as a channel layer of an FET, and a gate electrode 4 is provided on a region with a low concentration of dopant located over the high dopant concentration region 10. Thereby, the mutual conductance is increased and FET characteristics such as noise factor or power gain are improved. |
