This Project aims to produce a graphical user interface (GUI) for Matlab programs written by Dr. J. S. Marsland as part of his research into the excess noise factor in avalanche photodiodes (APDs). APDs amplify amplify photo-generated currents by the process of impact ionization; however this a random process which results in additional noise quantified by the excess noise factor. The GUI will then be used to compare this research work with the research work of others e.g. the Monte Carlo calculations made by the research group at the French Aerospace Laboratory (ONERA). The graphical user interface will be produced by using the GUIDE package supplied with MATLAB software combined with MATLAB programs already written. Comparision with other research work will require the digitization of some graphs published in academic journals. The project is strongly related to the research undertaken in the Department of Electrical Engineering and Electronics at the University of Liverpool. The results prove that the excess noise can be significantly reduced by something called the dead space effect.