Impurity incorporation in InGaN grown by rf plasma-assisted molecular beam epitaxy

Abstract

Impurity incorporation into InGaN films grown by rf-plasma assisted molecular beam epitaxy was investigated using secondary ion mass spectroscopy. A factor of 3 increase in both oxygen and boron incorporation into InGaN films relative to GaN films at 600 °C was demonstrated, and a factor of 10 increase in oxygen relative to the detectable base line in GaN grown under optimal conditions. Oxygen incorporation is related specifically to the different structures of the gallium and indium wetting layers on the growth surface. It is also shown using secondary ion mass spectroscopy that the formation of the gallium wetting layer during GaN growth is disrupted by the presence of excess indium; increased oxygen incorporation was observed during growth with an incomplete gallium wetting layer and indium on the growth surface. This study demonstrates the profound impact of surface atomic structure on impurity incorporation and reveals the protective nature of the gallium wetting layer as compared to the indium wetting layer during growth by rf-plasma assisted molecular beam epitaxy.