Heat transport under a large temperature gradient is a topic of much current interest. In order to develop methods for removing implantation damage in ion-implanted materials and, also, to produce metastable compounds and supersaturated alloys, it is important to achieve rapid melting and subsequent recrystallization of semiconductor materials. As heat flows in the solid phase, temperature profiles varying as much as 10 degrees per centimeter are not unusual. Under a large enough temperature gradient, heat conduction becomes anomalous, particularly near solid-liquid interfaces. The phenomenon is not yet fully understood but it is known that thermal conduction at high temperatures in semiconductors involves several processes, including some highly non-linear ones, that may contribute to the anomalous case. In this research project, Professor Gerald Mahan, in collaboration with Professor Francisco Claro of the Catholic University of Chile plans to investigate the trapping of carriers by a thermally induced gap-narrowing near the solid-melt interface in silicon and germanium. The band narrowing produces a confining potential that should be helpful in developing a theory of heat transport by electrons and electron-hole pairs. Additionally, the investigators are interested in the threshold for suppression of thermal conduction by temperature gradients, and in obtaining the space profile under steady heat flow near solid-melt interfaces. The combination of Professor Mahan's expertise with semiconductors and with nonlinear transport theory, with Professor Claro's complementary background in thermal transport techniques, creates a highly qualified team for addressing this complex and significant research. The mutual benefits of this collaboration fulfill an important criterion of the Science in Developing Countries Program.
