| Summary: | 碩士 === 國立成功大學 === 光電科學與工程學系 === 102 === In this study, high performance of Ga-doped ZnO (GZO) films have been prepared on sapphire substrates by the metal-organic chemical deposition (MOCVD). We focus on the optimization of the electrical and optical properties of GZO films by varying TMGa flow rate. It was found that the resistivity of as-deposited GZO thin films deposited with TMGa flow rate 10 sccm was 2.41×10-3 Ω-cm. After thermal annealing in 600 oC for 2 min in N2 ambient, the resistivity of GZO could be as low as 3.38×10-4 Ω-cm. It was attributed to the improvement of the GZO crystal quality, leading to an increase in electron concentration. It was also found that the optical transmittance of GZO thin films exhibited a high transparency above 97% at wavelength of 450 nm .
Ga-doped ZnO (GZO) were deposited by MOCVD to be the transparent contact layers(TCL) for GaN blue light-emitting diodes (LEDs). The contact resistance of GZO decreased with the annealing temperature increasing. It was also found that some Zn atom caused from the decomposition process diffused into the p-GaN surface of LED, which generated a stronger tunneling effect at the GZO/p-GaN interface and promoted the formation of ohmic contact. Moreover, contrast to the ITO-LED, a high light extraction efficiency of 77% was achieved in the GZO-LED at injection current of 20 mA. At 350 mA injection current, the output power of 256.51 mW of GZO-LEDs, corresponding to a 21.5% enhancement as compared to ITO-LEDs was obtained; results are promising for the development of GZO using the MOCVD technique for GaN LED applications.
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