Random-Walk EBIC Analysis of Carrier Diffusion in GaN Using a Schottky Nanocontact

Abstract We present the results of electron-beam-induced current (EBIC) measurements using a Schottky nanocontact formed by a tungsten needle placed on an intentionally undoped GaN layer grown by metalorganic chemical vapor deposition (MOCVD) on a sapphire substrate. The EBIC line profiles, extracted from the EBIC maps recorded in the vicinity of the contact, are used to identify key sources of uncertainty in estimating the minority charge carrier diffusion length in GaN. To complement the experimental analysis, a three-dimensional Monte Carlo (MC) model of charge carrier generation, diffusion, and EBIC formation is adopted and further developed to quantitatively investigate the evolution of EBIC line profiles at Schottky nanocontacts under varying sample and electron beam (e-beam) parameters. The simulations reveal that, for materials with short diffusion lengths such as GaN, the shape of EBIC line profiles at the space charge region (SCR) perimeter is significantly affected by the shape of the contact formed by the needle and e-beam energy. The findings highlight the limitations of the conventional EBIC-based diffusion length extraction method in materials with short diffusion lengths and support the advancement of EBIC methodologies for nanoscale Schottky contacts.