Compositional and structural characterization of indium nitride using swift ions

Abstract

Elastic recoil detection with swift heavy ion projectiles enables the direct and calibration-independent quantification of the N/In ratio and the impurity content of indium nitride thin films. The beam-induced dissociation of In and N can either be avoided or correctly be modelled, so that precise atomic fractions for In, N, O, C, and H can be determined. Results consistently indicate that state-of-the-art films tend to be nitrogen rich in contrast to the common perception that nitrogen vacancies are the reason for the native n-type characteristic of indium nitride. The magnitude of the nitrogen-excess measured for some of the films suggests that indium nitride contains nitrogen atoms or molecules interstitially. For structural characterization at the atomic scale, the radioisotope probe Indium-111 can be ion-implanted into indium nitride films. The interaction frequency of this probe has been measured as 28 MHz which is consistent with the frequencies for aluminium nitride and gallium nitride. Results suggest that independent of growth technique, indium nitride is characterized by a large and diverse number of defects. Annealing has been found to reduce the defect density. However, the small temperature range accessible for annealing is too limited to achieve a significant improvement of the material.