When the present samples were grown by means of metalorganic vapor phase epitaxy, the interface roughness which was caused by structural defects such as 2-dimensional islands, rough steps and multi-steps could be controlled by selecting suitable growth temperatures and substrate surface misorientation angles. Under conditions of growth without 2-dimensional islands or rough steps, the lateral and longitudinal sizes of the interface roughness could also be controlled by using variously misoriented substrates in order to determine the surface terrace width and step height. An investigation of the effect of interface roughness upon the resonant tunnelling peak current and peak-to-valley current ratio for resonant tunnelling diodes showed that the diode performance was markedly improved by reducing the width of the rough region to less than the Fermi wavelength of the electron; so that the electrons felt an apparently smooth interface.

M.Shinohara, H.Yokoyama, N.Inoue: Materials Science Forum, 1995, 196-201, 555-60