Wide bandgap semiconductors are a current area of interest for a new generation of high-temperature, high-voltage and high-power semiconductor-based electronics. Gallium nitride (GaN) is a promising candidate and is already extensively used in blue and UV LEDs[1,2]. Thin films are grown on substrates such as silicon and sapphireas to produce transistors with high electron mobility. However, these films suffer from large dislocation densities (108-1010cm-2)[3,4] due to the intrinsic strain of the substrate, resulting in devices with reduced reliability because of increased current leakage, disrupted electric field distribution and a premature breakdown of microplasma.
Therefore, novel methods of GaN device manufacturing using nanostructured systems such as nanowires and nanorods are a promising solution to minimise the presence of structural defects. Understanding how growth conditions affect the nanowire’s structure is important for future device fabrication, in particular the effect of annealing conditions on the dislocation density.
Here, we investigate unannealed GaN nanowiresgrown by metalorganic vapour phase epitaxy on Si substrates. The nanowires are doped with varying levels of Si, subjected either an N2 or N2+NH3 atmosphere upon growth.
The annealing process is seen to reduce dislocation density. Ex-situ annealing during growth shows a slight reduction in dislocation density. Figure 1 shows a comparison of dislocation density between an unannealed sample and a sample annealed at 900oC. Dislocation densities are measured to be 1.6×109 cm-2 and 1×109 cm-2 for unannealed and annealed nanowires respectively. The drop in dislocation density is, however, lower than expected for annealing at this temperature. In-situ heating experiments allow the direct observation of dislocation mobility during annealing, giving a valuable insight into dislocation bending.
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To cite this abstract:Mathew McLaren, Vitaly Zubialevich, Peter Parbrook, John Shen, Miryam Arredondo; Dislocation mobility in GaN nanowire arrays by in-situ heating in the TEM. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/dislocation-mobility-in-gan-nanowire-arrays-by-in-situ-heating-in-the-tem/. Accessed: July 23, 2021
EMC Abstracts - https://emc-proceedings.com/abstract/dislocation-mobility-in-gan-nanowire-arrays-by-in-situ-heating-in-the-tem/