| 摘要 |
PURPOSE:To be adapted for an FET by heat treating a semi-insulating GaAs substrate, altering the density distribution of impurity forming a deep level in a depthwise direction, then forming an active region by ion injection, and forming the carrier density stepwisely. CONSTITUTION:A GaAs substrate formed, for example, uniformly doping Cr to semi-insulating manner is heat treated, the Cr in the vicinity of the surface is diffused externally, and the Cr density in the vicinity of the surface is lowered as shown by a curve 2'. After Si ions are, for example, injected at 3.12<12>cm<-2> are 150keV to the substrate, it is protected with an Si3N4 film and is annealed, and the carrier density distribution of the trend of the curve 3' is prepared. Thus, the tail (curve 1') of the carrier density as in the case of using uniform Cr density for the substrate is eliminated in this manner and abrupt distribution is prepared, and accordingly the characteristics of the element can be stabilized, gm of the element is increased, and the noise is reduced. |
