| 摘要 |
PURPOSE:To realize a small positive threshold value with good reproducibility and uniformity by a method wherein an undoped semiconductor layer and an N<+> type semiconductor layer are formed on a semiconductor with a small electron affinity. CONSTITUTION:An undoped GaAs layer 12 (thickness 3-30nm) is provided between an undoped AlxGa1-xAs layer 3 and an N<+> type GaAs layer 5. As electrons leak out of the N<+> type GaAs layer 5 into the undoped GaAs layer 12 by thermal energy, the undoped GaAs layer 12 is charged negative. By this negative charge, a potential gradient is created in the undoped GaAs layer 12 along the direction of pushing back electrons from the undoped GaAs layer 12 to the N<+> type GaAs layer 5 and an edge of the conduction band of an undoped GaAs layer 2 is lifted in Fermi energy by energy DELTAE. Therefore, a threshold VTH takes a positive value DELTAE. |
