Direct Observation of an Ordered Phase in (11\bar20) Plane InGaN Alloy

A polar-dependent phase with spontaneous atomic ordering is found in a nonpolar (11 (2) over bar0) plane In(0.08)Ga(0.92)N film grown by metalorganic vapor-phase epitaxy. An atomic arrangement is a periodic sequence of group-III sublattices, Such as In(0.04)Ga(0.96)N/In(0.12)Ga(0.88)N, that is only observed in a nitrogen polar region through systematic transmission electron Microscopy investigation. Cathodoluminescence (CL) in the nitrogen polar region, i.e., spontaneously ordered atomic Structure of InGaN, reveals anomalous emission behavior, specifically an S-shape-like (increase-decrease) temperature dependence of CL peak energy. It is suggested that the spontaneous ordered atomic structure of InGaN plays the role of it localized center owing to band gap shrinkage, which has been reported in other III-V alloy systems. [DOI: 10.1143/JJAP.47.8783]