INTERFACE ROUGHNESS EFFECTS ON TRANSPORT IN TUNNEL STRUCTURES

Direct simulations of interface roughness effects on transport propert ies of tunnel structures are performed using the planar supercell stac k method. The method allows for the inclusion of realistic three-dimen sional rough interfacial geometries in transport calculations. For dou ble barrier resonant tunneling structures, we used our method to analy ze the effect of roughness at each of the four interfaces, and to test for sensitivity of transport properties to island size and height. Ou r simulations yields the following conclusions: (1) We find that scatt ering of off-resonance states into on-resonance states provides the do minant contribution to interface roughness assisted tunneling. Analyse s of scattering strength sensitivity to interface layer configurations reveals preferential scattering into Delta k parallel to approximate to 2 pi/lambda states, where lambda is the island size. (2) We find th at roughness at interfaces adjacent to the quantum well can cause late ral localization of wave functions, which increases with island size a nd depth. Lateral localization can result in the broadening and shifti ng of transmission resonances, and the introduction of preferential tr ansmission paths. In structures with wide and tall islands, it is poss ible to find localization over ''islands'' as well as localization ove r ''oceans.'' (3) The leading rough interface is the strongest off-res onance scatterer, while rough interfaces adjacent to quantum well are the strongest on-resonance scatterers. The trailing interface is the w eakest scatterer. (C) 1996 American Vacuum Society.