Defects in semiconductors

Dr. Huang's group has initiated a program to investigate basic issues related to rare-earth element (e.g., erbium) doped materials used for ultrafast optical communications.

These issues, such as doping of rare-earth elements with ion implantation, and impurity lattice site determination with ion channeling etc., are crucial for understanding the luminescence properties of rare-earth doped materials. In particular, we are trying to understand the atomic configuration of Er related centers in semiconductors, and to correlate these atomic structures with luminescence properties of Er-doped materials. Our recent work suggested that doping C impurity in Si tends to convert Er atoms from tetrahedral to hexagonal sites. Effects of nano-structures on Er luminescence are also being examined. Future experiments include polarized photoluminescence (PL) and high-pressure PL measurements for extraction of local symmetry and environments of Er centers. A further step is to combine experiments and theories for an understanding of fundamental processes involved in excitation/de-excitation of Er atoms in semiconductors.