Electrical properties of silicon surfaces and interfaces

Abstract

This work addresses two scientific challenges associated with diminishing device size. First, alternative surface passivation chemistries are investigated to meet the narrowing process tolerances for high quality silicon surfaces. Second, Si-based light emitting devices are studied to address a longer-term move towards photons instead of electrons for data transfer. A concerted effort is made to engineer environmentally benign solutions to these challenges. Highly effective Si( 100) surface passivation is achieved by immersing wafers in very dilute solutions of methanolic iodine. The electrical quality of Si surfaces is monitored in terms of surface recombination lifetime, employing radio frequency photo conductance decay (rfPCD) measurements. J/methanol treated surfaces are shown to have higher lifetimes and greater air stability than hydrogen terminated surfaces, while retaining comparable planarity and smoothness. Using XPS, UPS, and ATR-FTIR, the identity of the primary passivating surface species is ascertained to be a methoxysilane (Si-OCH3), and the most plausible passivation mechanism is deduced. Our results clearly illustrate the relationship between chemical passivation and electrical passivation. Thin films of visibly emitting silicon nanoparticles are fabricated using a pulsed laser ablation supersonic expansion technique. The electrical and electroluminescence characteristics of devices containing these films are shown to be controlled by carrier transport through the nanoparticulate silicon layer. A conduction mechanism encompassing both geometric and electronic effects most effectively relates the high resistivity with structural properties of the films. The observed temperature dependent PL, EL, and I-V characteristics of the devices are consistent with a model in which carrier transport is controlled by space-charge-limited currents or tunneling through potential barriers on a percolating lattice.