Device development for doping evaluation in nanowires using capacitance-voltage measurements
Abstract: This thesis aims to show the prospect of capacitance measurements over nanowire arrays as an evaluation method of the p-doping level in weakly p-doped p-n nanowires. The premise of the method is that there will be a high yield of statistical data regarding the doping level of the nanowires. The majority of the work carried out and presented in this thesis is however aimed at the manufacturing of a device suitable for said evaluation, and thus a range of different properties for materials were investigated. Due to early signs of parallel resistance in the device, allowing for an undesirably high back current, the disassociating isolator material as well as radial overgrowth of n-type InP was questioned. The isolating resist Cyclotene 3044-46 was thoroughly investigated before it was discarded due to its lacking electrical properties. The optional combination of SiO2 and photoresist S1818 was instead favored, albeit the resulting prolonged processing times. A device was created through various epitaxial, lithographic and etching techniques, creating a device inspired by the design used in nanowire-based solar cells. The design still needs further improvement, in order to eliminate flaws influencing the current through the device. Since the usage of Cyclotene would simplify the design and decrease the manufacturing time, further investigation into the origins of the poor electrical properties is of great interest.
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