Increased refractive indices in rare earth doped InP and In _0.53Ga _0.47As thin films

Rare earth (Gd, Eu, Er) doped InGaAs and InP layers were grown by liquid phase epitaxy (LPE). The refractive index of these layers was observed to increase with the addition of the rare earth ions. The observed increase could not be explained by changes in host composition as typically calculated from changes in lattice parameter. In fact, the refractive index was seen to increase (≈0.25) by an order of magnitude more than would be expected by the change in the lattice parameter (≈0.02). The increased refractive indices of InP layers due to Er-doping enabled waveguiding. These findings suggest that optically active waveguide devices can be fabricated from semiconducting hosts by simple rare earth doping.