| 摘要 |
PURPOSE:To prevent current from being reduced with the elapse of time even when drain source current is caused to flow to an HEMT element and to improve the high-frequency characteristics of the HEMT element by growing undoped GaAs on a Cr-doped semiinsulated GaAs substrate at the GaAs oxidative film scattering temp. or below. CONSTITUTION:A first undoped GaAs layer 2a is formed on the Cr-doped semiinsulated GaAs substrate 1 at the GaAs oxidative film scattering temp. (580 deg.C) or below. Then the temp. of the substrate 1 is raised up to 630 deg.C and an HEMT wafer is obtained by successively forming a second undoped GaAs layer 2b, an undoped AlxGa1-xAs layer 3 (x=0.22), an n-AlxGa1-xAs layer 4 (x=0.22) and an n-GaAs layer 5 on a first undoped GaAs layer 2a. |
