Lattice defects in InAs quantum dots on the GaAs „ 3̄ 1̄ 5̄ ... B surface

InAs quantum dots ~QD’s! grown by molecular-beam epitaxy on high-index GaAs(3̄1̄5̄)B substrates were investigated by in situ scanning tunneling microscopy. The shape of the QD’s is given by $110%, $111%, and $2 5 11%A bounding facets. The size distribution of the QD’s is quite broad, with the length at the foot ranging from 15 to 85 nm. Stacking faults and screw dislocations penetrating the QD’s are directly detected with atomic resolution at the QD facets. Many QD’s exhibit signs of coalescence. It is concluded that the wide size distribution, the occurrence of lattice defects, and the tendency to coalesce are indicative of incoherent, nonluminescent dots.