Title :
UV Electroluminescence and Structure of n-ZnO/p-GaN Heterojunction LEDs Grown by Atomic Layer Deposition
Author :
Chen, Hsing-Chao ; Chen, Miin-Jang ; Wu, Mong-Kai ; Li, Wei-Chih ; Tsai, Hung-Ling ; Yang, Jer-Ren ; Kuan, Hon ; Shiojiri, Makoto
Author_Institution :
Dept. of Mater. Sci. & Eng., Nat. Taiwan Univ., Taipei, Taiwan
Abstract :
Atomic layer deposition technique and subsequent rapid thermal annealing (RTA) were implemented to grow high-quality ZnO epilayers for the fabrication of n-ZnO/p-GaN heterojunction LEDs. The X-ray diffraction measurement reveals that the ZnO epilayer has high crystallinity with c axis orientation. Transmission electron microscopy images present that the ZnO layer is a single crystal, including only a few survivals of threading dislocations, which were generated in the GaN layer deposited by metal-organic chemical vapor deposition on the c-Al2O3 substrate and most of which were eliminated at the n-ZnO/p-GaN interface. An interfacial layer 4-5 nm thick caused by the RTA treatment was observed between the n-ZnO and p-GaN layers. Room temperature UV electroluminescence (EL) at 391 nm from ZnO was achieved at a low injection current about 10 mA. It is concluded that the competition between the ELs from the n-ZnO and p-GaN (around 425 nm) may be ascribed to the ZnO/GaN interface states coupled with the differences between the n-ZnO and p-GaN in carrier concentration and light emission efficiency.
Keywords :
II-VI semiconductors; III-V semiconductors; MOCVD; X-ray diffraction; atomic layer deposition; electroluminescence; gallium compounds; light emitting diodes; rapid thermal annealing; transmission electron microscopy; wide band gap semiconductors; zinc compounds; LED; UV electroluminescence; X-ray diffraction measurement; ZnO-GaN; atomic layer deposition; heterojunction; metal-organic chemical vapor deposition; rapid thermal annealing; size 4 nm to 5 nm; transmission electron microscopy images; Atomic layer deposition; Crystallization; Electroluminescence; Fabrication; Gallium nitride; Heterojunctions; Light emitting diodes; Rapid thermal annealing; X-ray imaging; Zinc oxide; Atomic layer deposition (ALD); LED; hetrojunction; zinc oxide;
Journal_Title :
Quantum Electronics, IEEE Journal of
DOI :
10.1109/JQE.2009.2025250