Electrical Properties of Erbium Doped Aluminum Gallium Arsenide

Progress towards understanding, and then using, semiconductors of the III-V compound family MS come fitfully in the past three decades, encouraging jests such as tMt gallium arsenide is the material of the future, and will always remain so. Yet despite some unfulfilled device expectations in the early years (hampered by primitive materials technology and by ignorance of the GaAs band structure and its consequences), gallium arsenide MS remained of interest to both scientists and technologists. From a practical point of view, sustained interest in GaAs was first rewarded by the GaAs injection laser, and then by various kinds of microwave devices. The technologies of crystal growth, epitaxy, and device processing have now all progressed to a point at which greatly enlarged horizons have appeared for GaAs utilization in integrated circuits and in optoelectronics. For example, several reports have now appeared in the literature on improved uniformity of semi-insulating (SI) GaAs used in the fabrication of high-speed electronic devices such as field effect transistors (FET) and integrated circuits after post growth annealing at temperatures near 800 C. For light emitting devices, on the other hand, doping of III-V semiconductor crystals with rare earth ions is an attractive approach. In contrast to other III-V optoelectronic devices, the luminescence (due to rare earth internal transitions) is practically independent of the III-V host crystal and of its band gap energy. In case of erbium, the luminescence occur at 1.54jJm wavelength. Therefore III-V:Er systems are interesting materials for application in optical fiber communication systems. In the last decade, several III-V semiconductor compounds doped with rare earth ions have been intensively investigated for their possible applications in optoelectronic devices. Many papers Mve reported the results of research on their photoluminescence spectra and optical properties. There is still very little known, however, concerning their electrical activity. Only a.few articles have been concerned with this aspect. Study of the electrical properties, when supported by photoluminescence research, is important in reaching an understanding of the mechanism for efficient activation of the luminescence observed. In this thesis we have tried to develop a better understanding of the transport properties of the alloy semiconductor Aluminum Gallium Arsenide systematically doped, by ion implantation technique, with erbium. We employed the Van der Pauw method to measure the electrical properties such as the Hall mobility, carrier concentration, carrier type and sheet resistivity. Our investigation reveals that most of the implanted erbium ions form complexes in the AIGaAs lattice and that majority of these ions reside on cation sites after annealing. Unfortunately our samples had a very high substrate impurity concentration, which prevented us from putting forward any assertive remarks regarding the change in electrical activity caused by these ions. The results reported here represent an initial or feasibility study of a small number of samples, undertaken to determine whether a more systematic (and costly) study is justified