The research activities of Randall Feenstra's group deal with structural and electronic properties of semiconductor materials and devices. A major tool used in the studies is the scanning tunneling microscope, which allows researchers to image the atomic structure of a surface and to perform spectroscopic measurements of the electronic energy levels. Many of the studies deal with semiconductor heterostructures consisting of multiple layers of different types of material, with the goal of understanding how the structure of the device (including imperfections and defects) determines its electronic properties. Growth of semiconductor heterostructures has been performed in Feenstra's laboratory using molecular beam epitaxy, for GaN in particular (a semiconductor with a relatively large band gap, used for blue light-emitting devices and for microwave transistor applications).
Most recently, his group has focused on the study of two-dimensional (2D) materials, including graphene and hexagonal boron nitride (h-BN).