Nano-scale Electrical Characterization of advanced semiconductors

Resume : Atomic Force Microscope is well-known, widely used technique for the topographic analysis of nanostructured materials. The use of the AFM tip as a probe of electrical properties allows enormous insights into material functionality at the nanoscale. In the present contribution two different cases relevant to the application of Conductive AFM to semiconducting thin films will be reported and discussed. First of all the electrical properties of intrinsic, B and P doped nc-Si:H (hydrogenated nanocrystalline Si) films grown by LEPECVD (Low Energy Plasma Enhanced Chemical Vapor Deposition) investigated by C-AFM will be dealt with. Notwithstanding this material is receiving an increased interest in the last years due to its promising photovoltaic properties, its electrical conduction at the nanoscale is still strongly debated. The maps present a clear evidence of enhanced conduction in the nanocrystals, while the (mainly amorphous) disordered tissue surrounding the nano-grains is mostly nonconductive. Thus, it can be concluded that the electrical conduction likely occurs via the conductive nanocrystals. The second case is the application of C-AFM to the investigation of lattice-matched Al0.84In0.16N/AlN/GaN heterostructures. These structures are interesting due to their applications as high electron mobility transistors (HEMTs) as due to the strong piezoelectric field a 2D electron gas density builds up at the GaN/AlN interface. Conductive and phase contrast AFM maps show several features that can be related to indium segregation at V-defects in InAlN. V-defects are directly associated with threading defects in wurtzite films.