Comparison of wurtzite and zinc-blende GaAs surfaces as possible nanowire side walls: DFT stability calculations

For further clarification of the reasons for the occurrence of wurtzite type GaAs nanowires we investigate the energetic stability of a great variety of reconstruction patterns for the relevant wurtzite surfaces (0001)A, (0001)B, 1 1 ¯ 00 , and 11 2 ¯ 0 by the DFT supercell method for the first time. A procedure to obtain absolute surface energies of the polar WZ surfaces is presented. Surface energies in dependence on the chemical potential are compared with those of the related zinc-blende structures. For the side walls 1 1 ¯ 00 /(112) or 11 2 ¯ 0 /(110), which play an important role for the stability of thin nanowires, the wurtzite structures are more stable than the related zinc-blende structures in a wide range of the chemical potential. From a comparison of the surface energies for WZ and ZB side walls it can be concluded that under strongly As-rich growth conditions only ZB type nanowires should be found and under less strongly As-rich conditions thin nanowires of the WZ type and thick nanowires of the ZB type should occur.