Electrical and optical isolation of GaN by high energy ion irradiation

Abstract

Unintentionally doped n-type gallium nitride (GaN) epitaxial layers grown by MOCVD technique on sapphire substrates have been subjected to 70 MeV nitrogen ion irradiation for various fluences. The sheet resistivity of GaN layer increases by 7 orders of magnitude for high fluence irradiation while its mobility and carrier concentration decrease as a function of ion fluence. The increase in sheet resistivity of GaN layer is explained with grain boundary controlled transport mechanism and the mobility degradation due to radiation induced charged scattering centers. Using deep level transient spectroscopy technique, a new deep level trap at 0.135 eV below the conduction band has been identified as a result of nitrogen ion irradiation. The photoluminescence emission of GaN layer decreases with increase in ion fluence and is completely quenched for high fluence irradiation.