Two-dimensional analysis of space-charge waves in a gallium-arsenide traveling-wave amplifier

The behavior of space-charge waves in a thin planar n-GaAs epitaxial layer grown on a semi-insulator GaAs substrate in the presence of a dc current is analyzed with allowance for electron diffusion. Two different modes traveling perpendicular to the electron flow are identified. Conditions for the oscillation of a planar Gunn-effect element are obtained. It is found that growth rate decreases as the thickness of the active layer is decreased below the wavelength of the space-charge wave, that this growth rate decreases at low frequencies due to longer wavelength and at high frequencies due to electron diffusion, and that Gunn oscillations are suppressed when the product of donor concentration and active layer thickness is less than a certain threshold value.