EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Selective area epitaxy of semiconductor heterostructures takes place on a crystal inside predefined patterns obtained by lithography inside an oxide mask. This technique allows the growth of complex structures which are highly scalable. As a typical example, we will consider InGaAs nanowire networks grown on InP. Based on physical information obtained from scanning probe microscopies, such as the shape, the orientation of the facets and the facet reconstruction, we will model the growth and explain the overall morphology of the nanowires by providing the effective diffusion length of group III elements. In a second part, we will be address the band alignment between the InGaAs nanowires and the InP buffer layer. We will introduce two different methods based on multi-tip scanning tunneling microscopy to measure the band offsets. In contrast to single probe tunneling spectroscopy, where electrostatic simulations of the tip-induced band bending are required to accurately determine the band offset, we will show that two-point probe tunneling spectroscopy and four-point probe transport measurements give a direct access to the band offsets. As the experiments are performed in ultrahigh vacuum, we will also address the contact resistance between the tips and the clean and well-ordered top InGaAs (001) facets. Finally, we will discuss the limitations of these techniques by providing other examples of multi-tip conductivity measurements performed with different heterostructure nanowires.