| 摘要 |
PURPOSE:To increase the carrier concentration of a two-dimensional carrier gas layer and avoid the influence of the deep impurity level of a semiconductor layer and avoid decline of a gate dielectric strength by a method wherein the undoped semiconductor channel layer of a high-speed field effect semiconductor device are provided between the 1st super-lattice and the 2nd super-lattice and a high concentration impurity is doped only into the well layers in those super- lattices. CONSTITUTION:An impurity is introduced into well layers 13B and 15B by a planar doping method. In other words, if only a molecular beam of Si is applied while a molecular beam of Ga is shut off after a GaAs layer is made to grow, the growth of GaAs is discontinued and only Si is made to grow with a very thin thickness. Therefore, by repeating such growths of GaAs and growths of Si proper times, GaAs layers can be doped with two-dimensionally. With this process, energy sub-bands are formed in the well layer 15B held between barrier layers 15A and in the well layer 13B held between barrier layers 13A and electron energy is elevated so that electrons can be easily injected into a channel layer 14 and the electron concentration of a two-dimensional electron gas layer 21 can be increased. |
