We demonstrate the growth by molecular beam epitaxy of a metal/semiconductor composite consisting of epitaxial semimetallic ErSb particles in a GaSb matrix. The ErSb nucleates in an island growth mode leading to the spontaneous formation of nanometer-sized particles. These particles are found to preferentially grow along a [011] direction on a (100) GaSb surface. The particles can be overgrown with GaSb to form an epitaxial superlattice consisting of ErSb particles between GaSb spacer layers. The size of the ErSb particles increases monotonically with the deposition. The carrier concentrations in the superlattices are found to be dependent on both the size and density of the ErSb particles. Smaller particles and closer layer spacings reduce the hole concentration in the film. (C) 2004 American Institute of Physics.

An investigation of the optical transmission properties of semimetallic ErAs films grown by molecular beam epitaxy reveals a maximum in transmission around 1.55 mu m. The semitransparent window extends from similar to 1.5 to 2.3 mu m. These films were found to have resistivities less than 7x10(-5) Omega cm and permit similar to 85% transmission for a 150 nm film and similar to 97% transmission for a 15 nm film with respect to a GaAs substrate at 1.55 mu m. These results suggest that ErAs may be a useful material for applications requiring transparent contacts from 1.5 to 2.3 mu m. Polycrystalline films of ErAs were grown on sapphire substrates to investigate optical properties of ErAs in the visible region. (c) 2006 American Institute of Physics.

We demonstrate subpicosecond photocarrier lifetimes at 1.55 mum in GaSb/ErSb nanoparticle superlattices grown by molecular beam epitaxy. Pump-probe measurements were made with a 1.55 mum mode-locked laser in transmission geometry to determine the photocarrier lifetime. The lifetime is found to be dependent on the size of the ErSb particles, amount of ErSb, and the distance between layers of particles. Through manipulation of these three parameters the photocarrier lifetime can be tuned down to less than 300 fs, the temporal limit of our experiment. (C) 2004 American Institute of Physics.