Bistable nanofacet structures on vicinal AlN(0001) surfaces

We demonstrate that the AlN vicinal surfaces with bunched steps are composed of ( 0001) and (1 (1) over bar 0m) nanofacets and have distinct stable structures for the growth-induced and thermal-etching-induced bunches. The index m is nearly four times greater for the growth surface than that for the etched surface. Furthermore, the stable nanofacet planes depend on the vicinal angles, suggesting that the growth and etching conditions are not primary factors to determine the nanofacet structures. The experimentally revealed step structures are well accounted for by the elastic balance model with consideration of the residual surface stress. (C) 2014 AIP Publishing LLC.