Influence of Mg doping on In adsorption and In incorporation in (In,Ga)N superlattices

TL;DR

This study investigates how Mg doping influences indium adsorption and incorporation in (In,Ga)N superlattices during plasma-assisted molecular beam epitaxy, revealing that Mg affects In content and Mg distribution through surfactant effects.

Contribution

It provides new insights into the role of Mg as a surfactant affecting In incorporation and Mg distribution in (In,Ga)N superlattices during epitaxial growth.

Findings

In content maximized when Mg is not supplied with In.

Mg concentration increases in (In,Ga)N layers compared to GaN barriers.

Mg acts as a surfactant, reducing Mg binding energy in presence of N.

Abstract

We present a detailed investigation of the mechanisms at play for the incorporation of In and Mg on the GaN(0001) surface during plasma-assisted molecular beam epitaxy (PAMBE). First, we have studied the kinetics of In desorption in the presence of Mg either without or with N supply from the plasma cell by quadrupole mass spectrometry (QMS) in the line of sight. Second, we have explored the effect of Mg doping at a different time along the cycle of (InN/GaN) supply repeated 10 times to form (In,Ga)N/GaN superlattices (SLs). By the complementary ex-situ investigation of these SLs by X-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS), we found that in monolayer-thick (In,Ga)N layer, the In content was maximized when Mg was not supplied simultaneously to In, but it drastically decreased otherwise. In contrast, the Mg concentration strongly increased in the (In,Ga)N monolayers compared to the GaN barriers. We attribute this finding to the surfactant effect of In for Mg, which decreases the binding energy of Mg in GaN in presence of N.