UCSB Physics Professor Herbert Kroemer was recently elected to the National Academy of Sciences. On April 29, Kroemer added this accomplishment to his list of acclaim, which includes an election to the National Academy of Engineering in 1997 and a Nobel Prize in Physics in 2000. UCSB now has 22 members in the NAS.
The NAS was established to advise the national government on science-related topics. Whereas awards are typically thought to be the result of a specific contribution, the NAS is “designed to be a recognition of an entire career of accomplishments,” said Matthew Tirrell, dean of the College of Engineering.
“Election to the NAS has a special distinction,” Tirrell said, “because it is a collegial gesture.”
Because nomination comes from fellow NAS members, Kroemer said election to the NAS has special meaning.
“It’s a tremendous honor [and] purely satisfaction… It is the biggest award one can receive in this country,” he said.
Kroemer said he has never wanted to make small advances. His goal is to develop technology so new that it has no application at the time of its introduction into the scientific community.
“Principal applications of any sufficiently new and innovative technology have always been and will continue to be applications created by the technology,” he said.
This view led Kroemer to develop semiconductor heterostructures. Semiconductors are chemical elements within a special class of electronic materials. One example, silicon, is best known for its wide use in computer chips. Compound semiconductors are conductors utilizing multiple chemical elements, such as gallium and arsenic. The only way two elements like gallium and arsenic can be bound to form a compound semiconductor is through the use of heterostructures such as those Kroemer has developed.
Semiconductors work by taking a bunch of non-conductive molecules like silicon, which create a lattice by each forming four stable bonds with surrounding silicon atoms, and then mixing in atoms like arsenic or boron, which have one too many or one too few electrons respectively to fit neatly into the lattice structure. The addition of such elements to silicon is called “doping.” The result is that the lattice is full of regions with either extra electrons or regions with too few electrons. Semiconductors with too few electrons are called p-type semiconductors, while semiconductors with too many electrons are called n-type. Because of these imbalances, electrons can begin to flow through the material. The lattice now conducts electricity, but not in large amounts, so it is called a semiconductor.
P-type and n-type semiconductors can be put together and arranged in creative ways to produce one-way valves for electrical currents called diodes or on-off switches called transistors. The introduction of semiconductors allowed for the introduction of small electronic devices. The only way previously to create a “semiconductor” was to pump electricity through a vacuum, which is relatively non-conductive. Vacuum tubes were used in electronics, but these were large and bulky. After the introduction of semiconductors, computers that had previously taken up entire rooms could suddenly fit on desks.
Through the development of a technology with no principal applications, a broad spectrum of uses has been created. This technology is used mainly in high-speed communication and optical electronics.
CD players, cell phones and nearly all devices associated with the information age utilize Kroemer’s technology.
“I have contributed my share,” he said.