9408479 Ruden The purpose of this work is to provide the first theoretical comprehensive study of electron and hole transport in GaN and ALGaN bulk and multiquantum well structures with the specific goal of determining the electron and hole impact ionization rates in these systems. From the knowledge of the transport properties of GaN/ALGaN obtained, the feasibility of developing a p-n junction GaN/AlGaN low-noise ultraviolet avalanching detector can be assessed. To date no compact, low-voltage, solid-state ultraviolet photodetector exists, In order to judge the utility of a GaN/AlGaN avalanche photodiode it is necessary to know the impact ionization rates in these materials. In this work, the electron and hole impact ionization rates will be theoretically determined using ensemble Monte Carlo simulations which include the full details of the conduction and valence bands calculated numerically from the pseudopotential method. A new formulation of the impact ionization transition rates will be included in the Monte Carlo simulators which takes into account the k-dependence of the transition rate providing a first principles determination of the carrier ionization rates. Using this technique, the electron and hole ionization rates will be calculated in bulk GaN, AlGaN and in related multiquantum well and superlattice structures. The calculated results will provide the first assessment of GaN/AlGaN for use in p-n junction APDs for ultraviolet detection. In addition, the refinement of the simulation tools used in this study will have significant impact on modeling other devices. Some possible devices whose design and optimization can be aided by the development of the proposed simulators are low noise, high gain photodetectors for high data rate communications, new APD designs for detection of wavelenghts from the ultraviolet to the infrared, and ultra-low noise IMPATT diodes. This study is a collaboration between researchers at Georgia Institute of Techology and University of Minnesota. ***
