Towards experimental identification of vacancy complexes in InN

Abstract

In this contribution we present ab initio calculations of positron states and annihilation at vacancies and vacancy complexes in InN. Momentum distributions of annihilating electron-positron pairs in indium (V In ) and nitrogen vacancies (V N ) as well as mixed vacancy clusters are calculated. Based on the modelled data the possibility of their experimental detection and distinction using positron annihilation spectroscopy is discussed. No localization of the positron density is found for isolated V N and V N clusters of up to 4V N . On the other hand, V In and mixed vacancy clusters act as efficient positron traps in InN. While the calculated momentum distributions for the divacancy and V In are quite close, mixed vacancy clusters which contain one V In and two or more V N show well distinct spectra, that could be distinguished in suitable positron annihilation experiments.

Identifying vacancy complexes in compound semiconductors with positron annihilation spectroscopy: A case study of InN

“…The induced uncertainty could in principle cause difficulties for the exact defect identification, as small differences between the different lattice directions are present. 31 Nevertheless, these are minor compared to differences between the calculated spectra of different defect complexes and hence pose no problem in our case. This counts especially when interpreting changes in the momentum distributions rather than absolute values.…”

“…We compare the experimental spectra to computational momentum distributions integrated over the m-plane. The induced uncertainty could in principle cause difficulties for the exact defect identification, as small differences between the different lattice directions are present 31 . Nevertheless, these are minor compared to differences between the calculated spectra of different defect complexes and hence pose no problem in our case.…”

“…25 The exact charge state of defect complexes is often unknown in experiments, hence it is not safe to be assumed without further proof. On the other hand, only considering the positron-induced forces 31 leads to an overestimation of the outward relaxation. Nevertheless, careful testing showed that the effects of additional charge and localized positrons on the annihilation characteristics can be neglected compared to changes between different defects.…”

Point defect evolution in low‐temperature MOCVD growth of InN

“…The observation of V In – n V N vacancy complexes near the interface speaks for a close proximity of V In and V N prior to complexing, and therefore for highly elevated concentrations of N vacancies in this area. Isolated nitrogen vacancies do not trap positrons in InN 15, 16 and hence escape detection with positron annihilation spectroscopy. Single V N are triply charged donors 20 and act as efficient donors in InN.…”

“…Selected results from previous positron studies in InN can be found in Refs. 10–16. In this contribution, we present a systematic study of the point defect landscape in MOCVD growth of InN with varying growth parameters.…”