The Department of Electrical Engineering

For the past twenty-three years our Molecular Beam Epitaxy laboratory has produced the world’s best gallium arsenide semiconductor hetero-structures to an ever higher standard.   These semiconductor structures have been used by scores of our collaborators around the world to facilitate new discoveries in new condensed matter physics, which would have been undetectable by scientists working with lower quality material. Our samples have contributed to research which was subsequently awarded a Nobel Prize in Physics, (the Fractional Quantum Hall Effect, 1998, Tsui, Stormer, and Laughlin), and three Buckley Prizes (1994, 2002, 2007) of the American Physical Society for outstanding contributions to condensed matter physics. 

 

The crystal-interface between semi-conducting gallium arsenide and semi-insulating aluminum arsenide is potentially among the most perfect material interfaces in all of nature. In appropriate hetero-structures carrier electrons can be made to accumulate in the semi-conducting gallium arsenide at this interface, thus forming a 2-dimensional layer with electron motion freely allowed in the plane of the layer, but with no movement possible perpendicular to the layer. Our gallium arsenide crystals have already shown the highest electronic mobility (a measure of perfection and purity) of any semiconductor for such 2-dimensional electron systems, and have become an indispensable experimental workbench for the discovery of new phenomena in semiconductor physics. To enable new discoveries in condensed matter physics, we are continually improving the perfection of the material and its interfaces by reducing the number of impurity atoms and crystal defects, and by designing new 2D structures that better screen the defects that remain. Each time we achieve a higher level of perfection in our gallium arsenide crystals, our magneto-transport and optics physicist collaborators have been able uncover important new physics insights in their fields of research. As electrons undergo less and less scattering with these impurities and defects, they interact primarily with each other in a collective fashion, forming new phases. This process has led to many surprising discoveries already. Continued progress in this fascinating field of low dimensional carrier physics requires samples with a higher and higher level of crystal perfection. 

 

Our laboratory at Princeton is dedicated to the growth of gallium arsenide crystal hetero-structures of the highest quality. In magneto-transport experiments these structures have already shown the highest electronic mobility (a measure of perfection and purity) of any semiconductor, and have become an indispensable workbench for the discovery of new phenomena in semiconductor physics.