Cho Receives Von Hippel Award
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Cho Receives Von Hippel Award
The Von Hippel Award, the Materials Research Society's highest honor, this year goes to Alfred Y. Cho, director, Semiconductor Research Laboratory at AT&T Bell Laboratories. He received the award "for pioneering work in the development of molecular beam epitaxy (MBE) and its application to new devices based on quantum wells and artificially structured materials." The Von Hippel Award is given annually to an individual in recognition of outstanding contributions to interdisciplinary research on materials. Al Cho has made seminal contributions to materials science and physical electronics through his pioneering development of the molecular beam epitaxy (MBE) crystal growth process. He took the emerging, somewhat esoteric process of MBE—a method for precisely controlling compositional profiles at the monolayer level—and turned it into a process of great scientific and technological significance. He demonstrated that MBE could be used to prepare epitaxial films with exquisite control and showed that these films could be the basis of devices with exceptional properties. His work has bridged many disciplines ranging from fundamental surface science, through epitaxial crystal growth, to device fabrication and testing. The capabilities of MBE have allowed new fields of materials research to develop. For example, the ability to precisely make quantum wells has had far-reaching impact from demonstrations of classroom physics to revolutions in laser devices for the electronics, information, and communications industries. Cho laid the foundations for the MBE process in the early 1970s through his use
of in situ monitoring of semiconductor crystal growth and epitaxy of GaAs. He was the first to observe the two-dimensional high-energy electron diffraction pattern of GaAs crystal growth, and the smoothing of the crystal surface, which ultimately formed the basis for successful growth of MBE materials and artificial structures. Beyond III-V materials, MBE also can be used for epitaxial growth of Si, Ge, metals, and insulators. The ability to form perfect alternating layers of GaAs and AlGaAs has led to the fabrication of modulation-doped superlattices with ultra-high electron and hole mobility which make the fastest transistors (as high as 140 GHz). Cho is responsible for many "firsts." In 1971, he fabricated the first MBE superlattice, and several years later created the first MBE microwave device—a GaAs voltage varactor. Among other devices he has developed using MBE are the IMPATT diode, field-effect transistors operating at microwave frequencies, lownoise mixer diodes used in radio astronomy, MBE double-heterostructure injection lasers operating continuously at room temperature, and heterostructure devices such as tunneling transistors based on bandgap engineering. Cho's open and generous personality expedited worldwide acceptance of MBE. Despite skepticism in the technological community, he refined the technique and shared information with all who would listen, not holding back details. He coll
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