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We have grown the high quality AlGaN/GaN heterostructure by plasma-assisted molecular beam epitaxy. We obtained the mobility of two-dimensional electron gas of the AlGaN/GaN is 9300 cm2/Vs and carrier concentration is 7.9¡Ñ1012 cm-2 by conventional van der Pauw Hall measurement at 77K. The samples made of the AlGaN/GaN heterostructure were patterned to Hall bar geometry with a width of 20£gm by conventional photolithography. After the photolithography, the nanowire was fabricated by the process of focus ion beam (FIB), and the widths of nanowire were reduced to 900 nm, 500 nm, 300 nm, 200nm, 100 nm, 80 nm and 50 nm respectively. The SiO2 layer and Al electrode were deposed on the samples to form nanowired MOSFETs. We have studied the leakage current measurement on the AlGaN/GaN nanowired MOSFETs at 300K. On the 100 nm and 200 nm width of nanowires, we did not observe the leakage current for the gate voltage work range from -2.5 to 3.0 V and from -0.5 to 0.5 V respectively.

The fabrication characteristic of focused ion beam (FIB) for fused quartz was investigated. With the progress of nanotechnology, new technologies and devices are invented constantly. In nanofabrication, FIB has several advantages such as high material removal rate, high resolving power and direct fabrication in some selected areas without etching mask. Therefore, it had been studied in detail to fabricate nano-structures by FIB. In this study, we found out the effect of nano-machining by adjusting the parameters of FIB system such as: beam current, overlap, and dwell time. The fabricated features together with their surface morphology and profile were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). Results show that when beam current was smaller, overlap was 50% and dwell time was 10£gs could get best performance by FIB.

We have observed a large spin-splitting in device made of AlxGa1-xN/GaN quantum wires. Based on this observation, we proposed a new spintronic application, the spin-hall quantum-ring interferometer, by the spin-Hall effect, Rashba and Dresselhaus effects. This device we use the ICP Etch System to etch the contact pattern, and then use the Multi-Target Sputter to deposit the protecting layer, and then use the E-Beam Evaporator to make the contact. Finally, using the Focus Ion Beam, we fabricate the quantum-ring and gate successfully. This thesis is focused on discussing the design of the fabrication and try to solve the problem in order to be able to detect the signal of the quantum-ring interferometer at low temperature and high magnetic condition.

The Institute of Ion Beam Physics and Materials Research (IIM) is one of the six institutes of the Forschungszentrum Dresden-Rossendorf (FZD), and contributes the largest part to its Research Program \"Advanced Materials\", mainly in the fields of semiconductor physics and materials research using ion beams. The institute operates a national and international Ion Beam Center, which, in addition to its own scientific activities, makes available fast ion technologies to universities, other research institutes, and industry. Parts of its activities are also dedicated to exploit the infrared/THz free-electron laser at the 40 MeV superconducting electron accelerator ELBE for condensed matter research. For both facilities the institute holds EU grants for funding access of external users.

The current semiconductor device manufacturing requires more strict control of plasma etching. In this research, plasma etching was investigated through gas phase characterization and interface reactions. Hydrogen and nitrogen were added to Ar plasmas to manipulate the electro-physical properties that were measured by a Langmuir probe system. Hydrogen addition modified the EEDF (electron energy distribution function) by increasing the electrons in high energy range. Adding N2 formed a strong bi-Maxwellian distribution. Gas addition caused the transition between ohmic and stochastic heating. Ar-CH4-H2 and Ar-N2-H2 plasmas were also tested. Hydrogen atom beam was used on porous silicon dioxide based low-k films to remove silanol groups that were generated due to the damage of films during pattern transfer. At H2 atom beam process at 150 C moved close to 60% silanol groups were removed in less than 3 min with an etching rate of 15 A/min. The apparent activation energy was 2.4 kcal/mol. Hydrogen atoms reacted with Si-O-Si and methyl groups. The etching mechanisms of CH4/H2/Ar plasma for InP were analyzed by a beam reactor system. Sputtering yield was measured, threshold energy was approximately 60 eV. Inert ion beam assisted chemical reactions gave higher etching rate. The CH4 concentration had no strong effect on etching rate after 5%. Etching rate was not sensitive to temperature up to 150 C. The adsorption of methyl groups to the surface was proposed as rate limiting step. Chemical reaction effectively reduced the surface roughness.

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