金屬半導體介面之研究

Abstract

金屬半導體介面之研究 張俊彥 ABSTRACT /////// Carrier transport in metal-semiconductor systems has been analyzed in terms of the most accurate quantum transmission coefficients. The fieldenhanced redistribution of carriers in systems formed between a metal and two-valley semiconductor (such as GaAs) has also been considered. In addition, the effects due to image-force lowering, interface states, temperature, and impurity concentration have been incorporated in the transport analysis to give a coherent and unified treatment. The satuation current density Js for a given metal-semiconductor system is found to reach a minimum value at a particular doping e. g. for ptSi n-type-si system at 300°K the value of Js is 8×10-8 A/cm2 at a doping of 1014 cm-3,reaches a minimum of 6×10-8 A/cm2 at 1016 cm-3, then rapidly increases to 10+3 A/cm2 at 1020 cm-3. This fact indicated the importance of doping effect on the rectifying for ohmic behavior of the system. the room-temperature transition doping for breakdown in metal-silicon system occurs at 1018 cm-3, for lower dopings the breakdown is due to avalanche multiplication, and for higher dopings due to tunneling of carriers from metal Fermi level to semiconductor hand edges. For the two-valley system with low doping e.g. 1014 to 1016 cm-3 one obtains negative differential resistance in the reverse direction. the metal-silicon barriers are fabricated by planar technique with guard-ring structures to eliminate edge effects. Extensive experimental studies including current-voltage, capacitance-voltage, photoelectric, and differential conductance measurements covering doping range from 1014 to 1020 cm-3 and temperature fange from 77°K to 373°K give good agreement with the theoretical predictions. differentiation measurements at 4.2°K also reveal scatterings of phonons with interface stated ans phonon-phonon interactions between different valleys along the <100> axis.