A model for calculating impact ionization transition rate in wurtzite GaN for use in breakdown voltage simulation

摘要

A model for calculating impact ionization transition rate (IITR) in wurtzite GaN has been developedfor use in breakdown voltage simulations. The characteristic feature of the model is to calculateenergy-dependent IITR by taking a conduction band index into account. Depending on the bandindex, the IITR values calculated by the proposed model show spreading by three orders ofmagnitude in the electron energy range from 6.5 to 8 eV, while this spreading is totally disregarded inthe conventional model. An impact ionization coefficient is calculated based on a full band MonteCarlo simulation which incorporates IITRs by the proposed model. The calculated impact ionizationcoefficients by the proposed model exhibit better agreements with those by the rigorous model.The proposed model is applied to the calculation of breakdown characteristics for AlGaN/GaNHEMTs and demonstrates a higher breakdown voltage by about 30% than that by the conventionalmodel.