Properties of hydrogen molecules in semi-conductors

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Hydrogen is now considered as one of the most important and well-understood impuirties in semiconductors though the 'simplest' possible H-related defect - H2 - was detected only in Si and GaAs and remains one of the less studied ones. The most unusual thing about H2 is that para (I = O) nuclear spin state of interstitial H2 in Si is not stable with respect to room temperature annealing and illimination with the bad gap light. This recently found phenomenon was tentatively explained by different diffusion rates of H2 in different nuclear spin states. Thus, detailed investigation of the H2 diffusion is the first task of the proposed project. In Si, Ge and GaAs high concentrations of hydrogen create extended planar defects called platelets. Under certain conditions these plavelets may hold H2 gas under high pressure. Two possibilities exist if this novel two-dimensional Bose system is cooled down to appropriate temperatures. Depending on the interacting potential between the molecules and the host, the H2 gas either forms a 2D crystalline structure or experiences Bose-Einstein condensation. Both possibilities are very attractive from a scientific point of view, making the study of 2D H2 gas a major task of the project. Raman scattering and Fourier tansform infrared spectroscopy are techniques to be employed to fulfill the goals outlined above.