Development of Monte-Carlo simulations for III-V semiconductors employing an analytic band-structure

• Main Author: Naylor, Daniel Robert
• Other Authors: Dyson, Angela
• Published: University of Hull 2012
• Subjects: 530; Physics
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.561042

The thesis is primarily concerned with the III-V-N semiconductors Gallium Nitride (GaN) and the dilute nitride Gallium Nitrogen Arsenide (GaNAs) and the effect that the band structure has on electron transport in these materials. Ensemble Monte-Carlo algorithms are developed in order to determine the electron transport properties of these materials, coupled with derived expressions for a novel band-structure approximation based on the cosine form that incorporates the inflection point in the Γ valley. The algorithm is validated by comparison of the output of the simulation with the well characteristics of other III-V semiconductors, and the new band-structure approximation is validated through comparison of the generated characteristics with experimental work and the output of the balance equations. Characteristics for GaN (bulk and in a 1D device) are presented, with excellent agreement with other works. It is found in bulk systems that there is the possibility of a significant number of negative-effective mass states occurring in GaN, dependent on inter sub-band (Γ- L-M) energy separation, and that these states have a noticeable effect on the characteristics of the system, both equilibrium and transient, particularly on the occurrence of the negative differential velocity in the velocity characteristics. A proof-of-concept algorithm for a 1D device code incorporating GaN is also presented with favourable results. Two models for bulk dilute GaNAs are used, one based on the Nitrogen Scattering model to measure the dispersive effect of N impurities, and one modeling the lower E−band from the BAC model with the cosine band-structure approximation to measure the distortive effect. Both models are used to generate equilibrium and transient characteristics for the material and we find that we have good agreement with recent works, particularly with the nitrogen scattering model.