Devices based on III-V compound semiconductors (e.g., GaAs, InP, GaN, etc.) have fueled the growth of the multibillion dollar telecommunications industry, making possible such technologies as fiber-optic communications, cellular phones, direct broadcast satellite TV, and global positioning systems. Unlike silicon-based devices, which are produced primarily by ion implantation techniques, the III-V device structures must be formed by depositing one plane of atoms after another until the entire structure is grown. Necessarily, III-V device fabrication occurs solely at a semiconductor surface. The better one can control and manipulate the motion of atoms on surfaces, the more sophisticated the devices structures one can make. In order to better understand the surface processes important to device fabrication, we have combined, for the first time, the state-of-the-art in III-V [(Al,Ga,In)-(As,P)] structure growth using molecular beam epitaxy (MBE) with the powerful atomic-scale surface characterization of scanning tunneling microscopy (STM).

Our current research interests can be conveniently classified into three areas. First, by taking STM images of a growing surface and using simple counting algorithms we can learn about the fundamental processes of growth: adsorption of new atoms on surfaces, single atom diffusion, nucleation of atoms into stable islands, and the growth of existing islands. Second, by replacing the normal metal STM imaging tip with a ferromagnetic metal, we can study the spin-dependent tunneling properties of the electron at the scale of an atom. In particular, we can identify which atomic-scale structures efficiently scatter the electronís spin. This project is geared toward the development of a new transistor which utilizes both the charge and spin of the electron to yield novel electronic properties. Third, we have combined a laser-interferometer system with our STM which allows us to measure optical properties of these technologically important surface structures with resolution down to the atomic scale.

As devices continue to shrink, conventional characterization techniques are increasingly ineffective in identifying factors relevant to device failure. However, since the invention of the STM, individual atoms may be viewed on a wide variety of systems and surfaces. Through the unique combination of MBE device growth and STM characterization, significant progress in the development of next generation devices can be achieved.