Correlated Structure-Property Investigation of Ultrathin InAs Nanowires

Sammanfattning: III-V semiconductors are a profound part of the optoelectronics industry and new developments in alloy compositions and architectures are constantly emerging. Lowdimensional semiconductors, such as nanowires (NWs) have shown to have improved characteristics in certain areas such as enhanced light absorption and can furthermore be integrated on Silicon (Si) plattforms and are thus predicted to be a key component in future nanoelectronic and nanophotonic applications and devices. InAs is an alloy exhibiting a very low bandgap giving it characeteristics such as low effective mass and ability to detect and emit light in the long-wavelength regime. Furthermore, when shrinking the size of the NW, quantum confinement occurs at an earlier stage in comparison to other alloys exhibiting larger bandgaps, which is a property useful to be able to tune the emitted wavelength in the NWs or as a future NW solar cell applications where the quantum confinement and splitting of bands can act as a photomultiplicator, creating high-efficient solar cells. In this thesis, NW growth using catalystfree site-selective area epitaxy (SAE) in molecular beam epitaxy (MBE) are performed and the growth aspects to achieve ultrathin InAs NWs are investigated. Electron-beam lithography (EBL) is used to open holes in a SiO2 on top of a silicon wafer wherein the wires nucleate and grow self-induced. The electron beam dose used as well as the distance between the exposed areas (pitch) was found to have a strong impact on the obtained size and yield of the NWs. By furthermore varying the growth time we show that the diameters of the NWs can effectively be tuned between <30nm to over 100nm to achieve wires in the desired dimensions with a high yield. These wires are then characterized in µ-Photoluminescence (µPL), where the diameter is correlated to the obtained PL emission and possible quantum confinement and other effects impacting the spectrum.