Unintentional Ga incorporation in metalorganic vapor phase epitaxy of In-containing III-nitride semiconductors

We prepared InAlN barrier layer films on GaN buffer layers using the metalorganic vapor phase epitaxy (MOVPE) method and investigated the InAlN/GaN heterointerfaces. Secondary ion spectroscopy experiments revealed that a quaternary alloy of InAlGaN is grown on GaN even when trimethylindium (TMln) and trimethylaluminum (TMAl) are exclusively supplied as group-III precursors, indicating that Ga is unintentionally incorporated into the InAlN layers. This Ga incorporation is also observed in InGaN/GaN heterostructures. Our systematic investigations of the growth condition dependence, such as the TMln flow rate, indicate that the Ga is supplied by a transmetalation reaction between TMln and residual Ga on the flow distributor in the reactor. Here, we show that the Ga incorporation can be eliminated by adopting an elaborate growth sequence, including reactor cleaning and regrowth processes. This study provides guides for designing the MOVPE reactor configuration, as well as the growth sequences, for the growth of device structures with In-containing nitride layers. (c) 2013 Elsevier B.V. All rights reserved.