Electrical characterization of ion-beam induced damage in GaN

Abstract

Ions with different energies have been used to modify the properties of semiconductors. In particular, these modifications have included altering the electrical properties of semiconductors. The ion-solid interactions during ion irradiation can induce electrically active defects in these materials. These defects can be beneficial or detrimental to the device, depending on the use of the device. In this study, deep level transient spectroscopy (DLTS) was used to study electrically active defects in gallium nitride (GaN) after various ion-processing methods. These ion bombardment processes included ion implantation and irradiation. Low, medium, and high energy ions were used during these procedures. (In this study, ion implantation implies medium energy ion bombardment while ion irradiation implies high energy ion bombardment.) Electron beam exposure (EBE) is a method that was used for exposing GaN to low ion energy conditions. In this method, GaN was exposed to metal evaporation conditions without evaporating the metal. In the second case GaN was exposed to 360 keV Cs ion implantation. Lastly, Xe ions with energy 167 MeV were irradiated onto GaN. Different species of defects were observed in each case. Only one defect was observed in the EBE study and had an activation energy of 0.12 eV. This defect is similar to defects obtained in other studies, which used different irradiation methods, such as electron, proton and gamma irradiation. The Cs ion implantation yielded a defect with activation energy of 0.19 eV. A comparison was made to defects obtained using other processing techniques, which included electron beam deposition and various ion implantations. Lastly, Xe irradiation yielded two defects with activation energies of 0.07 and 0.48 eV. Both these defects were also compared with those obtained in other studies. The former was similar to a defect predicted by modelling while the latter was similar to a defect obtained by In doping. It was found that all the processing techniques used in this study induced electrically active defects as measured by DLTS. It was found that the defects measured in this study had similar characteristics to those found in other studies, whereby different processing methods were used. It is therefore deduced that the defects are not related to the ion, but rather are intrinsic defects or defects related to impurities in the GaN. This shows that different energies of ions lead to different defects forming in GaN. This understanding will contribute to improved quality and reliability of devices fabricated on GaN in applications ranging from radiation detection to communications.