The Bandgap of InN Gave Rise to Animated Discussion at IWN-04
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CONFERENCE REPORTS
The Bandgap of InN Gave Rise to Animated Discussion at IWN-04 The 2004 International Workshop on Nitride Semiconductors (IWN-04) was held July 19–23 at Sheraton Station Square by the Monongahela River in Pittsburgh, Pa. Workshop Chair Randall Feenstra (Carnegie Mellon University) worked closely with the Program Committee, chaired by Tom Myers (West Virginia University), and the International Advisory Committee, chaired by Russell Dupuis (Georgia Institute of Technology), to put together an extensive program with topics ranging from recent developments in ultraviolet light-emitting diodes (UV LEDs) and high-electron-mobility transistors (HEMTs) to advances in growth and characterization techniques, to the bandgap of InN. The program encompassed two parallel sessions with eight invited talks and more than 400 oral and poster presentations delivered to 500-plus attendees. Published proceedings of the workshop will appear in a special volume of physica status solidi. The workshop began with plenary talks on UV LEDs (A. Khan, South Carolina University) and ferromagnetism in III–V and III–N semiconductors (H. Ohno, Tohoku University). Khan reported on how innovations such as the group’s novel growth technique of migrationenhanced metalorganic chemical vapor deposition and the use of a new micro-
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Randall Feenstra (Carnegie Mellon University), chair of the 2004 International Workshop on Nitride Semiconductors (center), meets with Program Committee chair Tom Myers of West Virginia University (right) and International Advisory Committee chair Russell Dupuis of Georgia Institute of Technology (left) during the welcome reception.
pixel geometry have resulted in the successful production of LEDs emitting down to 250 nm. External quantum efficiencies of such deep-UV LEDs are still low due to dislocations in the AlGaN; however, future progress is expected to open up yet another billion-dollar industry to the nitrides, that of biomedical sensors. Ohno
reviewed the properties of III–V-based magnetic semiconductors, describing, for example, how magnetic properties can be electrically controlled in such materials— magnetization reversal can be obtained through current-induced domain wall propagation. In the session on lasers, J. Heffernan of Sharp Laboratories Europe, U.K., gave a detailed report on the company’s pioneering work on InGaN multiple-quantumwell laser diodes grown by molecularbeam epitaxy (MBE). He reported that their threshold voltage is now down to 10 V, with a current density of 7 kA cm–2 (200 ns pulses; duty cycle, 10%). Improved thermal management should lead to further improvements in performance, he said. Advances in high-power microwave devices also attracted attention—in particular, Cree’s spectacular results from field plate devices, with over 30 W/mm continuous-wave power density and over 50% power added efficiency. J. Speck of the University of California—Santa Barbara discussed the advances in MBE for the growth of GaN-based electronic devices, with results equal to or improving u
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