| Summary: | 碩士 === 崑山科技大學 === 電子工程研究所 === 98 === We mainly discuss the contact characteristics of p-GaN and metal in this thesis. We hope to get high reflectivity and low specific contact resistance, choose the optimized structure and annealing condition, combine the device with silicon substrate by wafer bonding and use laser lift-off technique to remove the sapphire substrate, finally the vertical GaN-based light-emitting diodes were fabricated successfully.
We fabricate four different structures of ohmic contact, they are Ni/Ag/Ni/Au, Ni/Ag/Ti/Au, Ni/Ag/Ni/Ti/Au and Ni/Ag/Ni/W/Ni/Au, respectively. We try to compare the optical and electrical characteristics to each other under different annealing temperature and time, finally find the Ni/Ag/Ni/W/Ni/Au has better reflectivity, specific contact resistance and smoother surface. Among these samples, we find the Ni/Ag/Ni/W/Ni/Au (10/150/30/70/10/150 nm) structure has higher reflectivity of 93.07%(@450 nm) and lower specific contact resistance of 4.69×10-3Ω-㎝2 under 400℃ annealing for 30 minutes, so we use this metal structure and annealing structure to fabricate the vertical GaN-based light-emitting diodes finally. Under 350mA current injection, the forward voltage (Vf ) of our fabricated device is 3.67 V and the light output power is 256.5 mW.
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