First-principles investigation of nonradiative carrier capture by defects in GaN

Wide-bandgap semiconductors including gallium nitride (GaN) have been indentified as radiation-resistant options for extreme applications. Displacement damage forms point defects in the crystal structure with corresponding energy levels in the bandgap. These can act as trap or recombination sites for the charge carriers responsible for current transport in the devices, resulting in subsequent decreases in carrier density and carrier mobility.¹

The goal of this work is to understand the impact of nonradiative carrier capture by defects in GaN on device performance. Previous work developed a first-principles approach to modeling nonradiative carrier capture, demonstrated with calculations on a C substitutional atom on a N site.² Using this defect as a benchmark, capture coefficients were found for each charge transition for native point defects and a divacancy in GaN. Electron capture from positive to neutral by the Ga interstitial and N vacancy were identified to have high coefficient values, as did neutral to positive hole capture by the Ga vacancy. Antisites and higher charge state defects generally had low values. Carrier capture rates then determine which processes are expected to significantly impact device performance.

1.    Fleetwood, D. M., Zhang, E. X., Schrimpf, R. D., and Pantelides, S. T. Radiation effects in AlGaN/GaN HEMTs. IEEE Trans. Nucl. Sci. (2022).

2.    Alkauskas, A., Yan, Q., and Van de Walle, C. G. First-principles theory of nonradiative carrier capture via multiphonon emission. Phys. Rev. B (2014).