This award is to support rare-earth doping of semiconductors for the possibility of realizing novel types of optoelectronic devices and sources. The wavelength of the rare-earth related 4f emissions practically does not depend on the bandgap energy of the host crystal and is immune to temperature variations. However, the gain of the lasers is not high and the rare- earth doping and excitation process is not clearly understood. We propose a systematic investigation of GaAs and InP-based semiconductors - mainly GaAs and InGaAsP - doped during MBE by Er and by implantation of Yb. The experiments will include time-resolved luminescence with both resonant and non-resonant excitation, conductance and admittance spectroscopy to characterize deep levels, low and high field transport and reflectance measurements. It is expected that these experiments will improve the basic understanding of the doping process, changes in the material radiative and non-radiative properties, and the temporal characteristics of the rare-earth related transitions. The latter are particularly important for the design of high-speed pulsed lasers. The PI also proposes the use of rare-earth doped materials in a couple of novel laser structures. In the first the active medium is a selectively doped MQW with narrow rare-earth doped wells. In the second, a cascade of avalanching carriers is made to resonate with the rare-earth transition energy, thereby causing a large non- equilibrium distribution through collision excitation.
