Spontaneous InAs quantum dot nucleation at strained InP/GaInAs interfaces

We present a cross-sectional scanning-tunneling microscopy investigation of twofold stacked InAs quantum dots in InP, between layers of GaInAs. The dots are vertically aligned, and images with atomic resolution show that the dots consist of pure InAs. Despite the intended twofold stacking of dots, three dots were often found in the stacks. The third dot formed immediately on top of the final InP layer, at the InP/GaInAs interface. Atomically resolved images of these spontaneously formed dots indicate that they also consist of pure InAs. The effect is discussed in terms of phase segregation of GaInAs and arsenic-phosphorus exchange reactions. (C) 2003 American Institute of Physics.