9220382 Neugroschel The Si/Ge1-x/Si heterojunction bipolar transistor (HBT) is one of the most promising devices for manufacturing Si-based ultrafast VLSI and ULSI circuits. The GexSi1-x layer, used for the base of the transistor, can be grown by slightly modifying the Si technology and taking advantage of the complete miscibility of Ge and Si to tailor the profiles of the energy gap for optimum performance. The proposed work will concentrate on the investigation of the fundamental electronic properties of the composite GexSi1-x strained thin layers grown on silicon substrate. The properties to be investigated are the transport parameters important primarily to the performance of the Si/GexSi1-x/Si HBT, but useful also for other applications. These include the minority-carrier mobility (or diffusivity) and lifetime, energy gap, GexSi1-x junction. The investigation will be made as a function of growth conditions, the layer thickness and compostion (Ge content x), strain and strain relaxation (via annealing), dopant impurity concentration and temperature. It is expected that the proposed research will significantly enhance the present understanding of the bulk and interface properties of the Si/GexSi1-x heterostructures, and will allow optimization of device to reach higher performance not attainable using the current empirical approach.
