TWINNING PROGRAM WITH ESTONIA, LATVIA, AND LITHUANIA

Arturas Zukauskas of the Institute of Materials Science and Applied Research of Vilnius University arrived for a month-long visit to Rensselaer Polytechnic Institute in March 2000. During his stay, he and his host, Remis Gaska, initiated their joint work in the field of nonlinear spectroscopy of AlInGaN-based materials and heterostructures. Zukauskas had the opportunity to examine the latest literature on optical properties and nonequilibrium phenomena in wide band gap nitride semiconductors. In addition, Zukauskas had brought with him some experimental data on optical properties of AlInGaN quaternary alloys, and he discussed his findings with Gaska and other colleagues at RPI. Their research, which involves applications of strain energy band engineering to optimize heterostructure field transistors and light emitting structures, has focused specifically on the effects of incorporating small amounts of indium into AlGaN. So far, they have found that in comparison with reduced-temperature-grown AlGaN, the quaternary AlInGaN exhibits significantly improved material quality and optical properties.

As a result of their work during 2000, Gaska, Zukauskas, and several colleagues at each of their institutions have produced two joint publications. They have also presented their findings at conferences in the United States, Poland, England, Lithuania, and Japan. As for 2001, Zukauskas began his second visit to RPI on February 1, and Gaska plans to travel to Vilnius in September.

Update on Activities During 2001

The year 2001 was a busy and productive one for Remis Gaska and his Lithuanian colleague Arturas Zukauskas of the Institute of Materials Science and Applied Research of Vilnius University. The researchers made three exchange visits beginning with a three-month stay by Zukauskas at Rensselaer from February through April 2001 (the first month was sponsored by the Twinning grant, with the other two months being covered by RPI). During his visit, the Lithuanian researcher helped to develop an experimental setup for nonlinear spectroscopy of III-Nitride materials and continued working with Gaska on optical characterization of semiconductor materials and applications of these materials in solid-state lighting. Gaska made two visits to Vilnius University, one in March and the other in August 2001, during which he participated in research seminars as well as data analysis and related discussions.

As a result of their two-year project, this team has now published eight technical papers and made presentations at twelve conferences, including a tutorial on solid-state lighting at the Fall Material Research Society Meeting in Boston in November 2001. Although their Twinning grant has now ended, Gaska and Zukauskas have a full agenda for collaboration in 2002, using other funding sources. One of Zukauskas’ colleagues from Vilnius will visit RPI for three months beginning in April 2002, and Zukauskas himself is expected to return to RPI for two or three months beginning in September. In cooperation with another scientist at RPI, Michael Shur, the two Twinning partners have also signed a contract to publish a book entitled Introduction to Solid-State Lighting in 2002. In January 2002, Gaska submitted a proposal to the NSF Major Research Instrumentation Program for the development of a wide-band-gap semiconductor nondestructive testing setup based on the optically-induced transient diffraction grating method. If the proposal is funded, Zukauskas’ group will be included as a subcontractor to develop one component of the equipment. Finally, Gaska and Zukauskas have begun drafting another proposal to NSF regarding the characterization of deposition, doping, and processing of high Al-content AlGaN and AlInGaN materials and structures for deep ultraviolet emitter applications. Thanks to the Twinning grant they received, this U.S.-Lithuanian team has built a strong foundation for productive ongoing collaboration.ember.