Influence of plasma species on the early-stage growth kinetics of epitaxial InN grown by plasma-enhanced atomic layer deposition

Abstract

Plasma-enhanced atomic layer deposition (PEALD) enables the epitaxial growth of ultrathin indium nitride (InN) films at significantly reduced process temperatures and with greater control of layer thickness compared to other growth methods. However, the reliance on plasma-surface interactions increases the complexity of the growth process. A detailed understanding of the relationship between the plasma properties and the growth kinetics is therefore required to guide the tuning of growth parameters. We present an in situ investigation of the early-stage PEALD growth kinetics of epitaxial InN within three different plasma regimes using grazing incidence small-angle x-ray scattering (GISAXS). The GISAXS data are supported by diagnostic studies of the plasma species generation in the inductively coupled plasma source as a function of the relative concentrations of the nitrogen/argon gas mixture used in the growth process. The growth mode is found to be correlated to the production of nitrogen species in the plasma, with high concentrations of the atomic N species promoting Volmer–Weber growth (i.e., island growth) and low concentrations promoting Stranski–Krastanov growth (i.e., layer-plus-island growth). The critical thickness for island formation, island center-to-center distance, and island radius are found to increase with ion flux. Furthermore, the island center-to-center distance and areal density are observed to change only during plasma exposure and to continue changing with exposure even after the methylindium adlayer is believed to have fully reacted with the plasma. Our results demonstrate the potential to control the growth kinetics during PEALD of epitaxial films by intentionally accessing specific regimes of plasma species generation.