UV Electroluminescence and Structure of n-ZnO/p-GaN Heterojunction LEDs Grown by Atomic Layer Deposition

• Published in: IEEE journal of quantum electronics Vol. 46; no. 2; pp. 265 - 271
• Main Authors: Hsing-Chao Chen, Miin-Jang Chen, Mong-Kai Wu, Wei-Chih Li, Hung-Ling Tsai, Jer-Ren Yang, Hon Kuan, Shiojiri, M.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2010; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Atomic layer deposition; Atomic layer deposition (ALD); Crystallization; Electroluminescence; Electronics; Exact sciences and technology; Fabrication; Gallium nitride; Heterojunctions; hetrojunction; LED; Light emitting diodes; Optoelectronic devices; Rapid thermal annealing; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; X-ray imaging; Zinc oxide; Binary compound; Gallium Nitrides; Electroluminescence; Zinc Oxides; LED; Experimental study; X ray diffraction; Chemical vapor deposition; Single crystal; hetrojunction; Light emitting diode; Atomic layer deposition (ALD); Injection current; Transmission electron microscopy; II-VI semiconductors; Zinc oxide; Thermal annealing; Room temperature; Heterojunction; III-V semiconductors
• ISSN: 0018-9197; 1558-1713
• DOI: 10.1109/JQE.2009.2025250

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-Al 2 O 3 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.