Self-affine roughness effects on electron transmission and electric current in tunnel junctions

Interface roughness effects on electron transmission in tunnel junctions ar e investigated theoretically in the limit of thick barriers. The barrier ro ughness is described in terms of self-affine fractal scaling by the roughne ss exponent H, rms roughness amplitude w, and correlation length xi. For re alistic parameters diffuse transmission usually exceeds specular transmissi on. It is shown that for small roughness exponents (H < 0.5) the transmissi on coefficient increases with decreasing ratio w/xi. For large roughness ex ponents (or smoother interfaces at short wavelengths) the transmission coef ficient has a maximum at a certain value of the ratio w/xi. With increasing w/xi the tunneling current behaves similarly as the transmission coefficie nt. (C) 2000 American Institute of Physics. [S0021-8979(00)05814-X].