Change in Growth Mode of BGaN Layers Grown on GaN

Abstract

A change in the growth mode from Stranski–Krastanov one, which is characteristic of MOCVD grown GaN, to the laterally grown BGaN in the Volmer–Weber growth mode is described. This change in growth is evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of BGaN grown on GaN at high temperatures. It is postulated on the basis of SIMS and XRD results that this change in growth is initiated by the transfer of boron atoms from gallium substitutional to interstitial. The proposed mechanism for the observed growth change is related to the generation of nitrogen interstitials and subsequent reactions with boron interstitials, which result in the formation of a BN layer at the growth front. The observed large change in the growth mode is due to a lattice mismatch between the grown BGaN and the atomic layer of BN and stays behind the change to the Volmer–Weber growth mode. The consequence of the Volmer–Weber growth mode is the textural layer of BGaN. The textural character of this material is associated with large voids between grown BGaN “plates”. These large voids are responsible for the termination of threading dislocations propagating in the c-direction. It is also postulated that the blocked threading dislocations from the GaN underlayer and laterally grown BGaN layers along the a-directions are responsible for the decrease in defect concentration within these layers.

Keywords

• BGaN
• growth mode
• MOCVD epitaxy