| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 95 === The research in this paper was to use transparent and conductive ZnO films with Al nano-particles (Al doped ZnO, AZO) to increase the extraction efficiency of GaN-based LEDs. The AZO films were deposited by sputtering ZnO(99.99%) and Al(99.99%) targets simultaneously. Fixing the ZnO RF power of 100W and changing the Al DC power from 0 to 13W could deposit different Al concentration AZO films. The carrier concentration of AZO films after annealing would increase with increasing Al concentration at first. However, while the amount of Al was more over than the dissolution of Al in ZnO, the carrier concentration would decrease with increasing Al concentration and the excess Al would form neutral atoms and segregate. In this research, the AZO films with Al DC power of 0, 4.5, 7W would not have Al segregation and with Al DC power of 10 and 13W would segregate Al nano-partlcles. Before the different Al concentration AZO films were deposited on p-type area of LEDs, a thin AZO film (10nm) was deposited by e-gun system. This was due to the plasma of sputter would damage the transparent contact of LEDs. Then, different Al concentration AZO films (170nm) were deposited on p-type area of LEDs to compare the light intensity of LEDs. Before measuring the light intensity of LEDs, the bi-layer AZO films on and surround the p-type bonding metal was etched. Thus, the current spreading of AZO films would be removed and the different resistance of different Al concentration AZO films would not affect the light extraction efficiency of LEDs. The light intensity of LEDs deposited with AZO films with Al power of 0, 4.5, 7W increased 10~15% than conventional LEDs. This was due to the AZO films played a role of anti-reflection coating (ARC). The light intensity of LEDs deposited with AZO film with Al power of 10W increase about 30%. The AZO film with Al power of 10W had Al nano-particles. The Al nano-particles could scatter the light to change the direction of the light which formed total reflection at the interface of AZO and air and more light could be extracted. However, when the LEDs deposited with AZO film with Al power of 13W, the light intensity of LED decreased contrarily. This was due to the AZO film with Al power of 13W had too much and too large Al nano-particles to form serious back scattering. Finally, the current spreading function of AZO films was added to improve the light extraction efficiency of GaN-based LEDs further.
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