The presence of a magnetic field during anodization of Si in HF solution can drastically influence the resulting porous Si morphology. The effect of the strength of the magnetic field was investigated. The magnetic field enables the realization of non-percolating straight pores of diameters from 100 nm with n+-type Si to several micrometers for p-type Si, through depths as large as 100 μm, without any lithographic or pore initiation process. There is a clear enhancement of the pores aspect ratio when increasing the magnetic field strength, which enhances the collection of holes at the pore tips with respect to lateral pore walls. Thick, well-defined free-standing membranes can also been fabricated for applications such as bio-scaffold and filters.
The operational amplifier (op-amp) with high gamma irradiation capability of over 30 kGy have been fabricated by 4H-SiC MOSFETs for measuring instruments which are installed in nuclear power plants. The chip size was 0.7 mm x 1.0 mm, and they consisted of five n-channel MOSFETs and three p-channel MOSFETs on the same die. The output waveform after having irradiated 50 kGy at a rate of 60 Gy/hr was amplified without distortion. On the other hand, the offset voltage became unstable when gamma integral dose was beyond 30 kGy and it at 50 kGy increased to +7.2 mV. For reduction of gamma irradiation influence, we proposed the MOSFETs structure which has field plate (FP) electrodes connected to isolation layer electrically. We indicated that the proposal device had the potential of gamma irradiation capability of 100 kGy experimentally.
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