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Past Events
GaN/ZnO Heterojunction LEDs
| Speaker: | Dr. A.B. Djurišić |
| Affiliation: | Department of Physics, The University of Hong Kong, HKU |
| Date: | December 15, 2009 (Tue) |
| Time: | 5:00 -6:00 p.m. |
| Venue: | Lecture Theatre P4, LG1/F, Chong Yuet Ming Physics Building, HKU |
Abstract:
The direct wide band gap semiconductor ZnO has large exciton binding energy (60 meV) and its wurtzite crystal structure closely matches that of GaN, which is a conventional LED semiconductor. In addition, ZnO is chemically stable, non-toxic, low cost, and relatively abundant and it can be grown by simple, inexpensive methods such as electrodeposition. Due to the low lattice mismatch, p-GaN/n-ZnO heterojunction devices are of great interest. Also, LEDs based on 1D nanostructure are expected to give better device performance. Therefore, our work has been focused on p-GaN/n-ZnO nanorods based heterojunction. A variety of emission colors depending on the preparation parameters has been obtained, including devices with tunable emission from orange at 2.1 V over white at 2.5 V to blue at 2.7 V. Light extraction enhancement by random texturing using electrodeposited ZnO nanorods was also achieved. P-GaN/ZnO heterojunction devices with light extraction layer show an increase of 30-50% in emission intensity.
Coffee and tea will be served 20 minutes prior to the seminar.