| Summary: | 碩士 === 國立中央大學 === 光電科學研究所 === 90 ===
Low resistance and reliable ohmic contacts to both n- and p-type GaN:Ohmic contacts with low contact resistance are essential in improved GaN based on LEDs. For n-type GaN, ohmic contacts with low contact resistance have been achieved by several research groups, including our group . On the other hand, the contact resistance for ohmic contact to p-GaN was too high to need the requirement for GaN-based optical devices. According to our previous studies for (NH4)2Sx-treated Si- and Mg- doped GaN surface, we found that the original native oxide on the GaN surface was effectively removed by the (NH4)2Sx solution and a specific contact resistance of 5.0×10-5Ωcm2 for the Ti/Al nonalloyed ohmic contacts to (NH4)2Sx -treated n-type GaN can be obtained. Therefore, in this plan, high performance of ohmic contact with the (NH4)2Sx-treated p-GaN surface will be investigated.
In addition, conventional opaque metals were used as p-type electrode contacted with semiconductors in electronic and optoelectronic device. However, the resultant devices suffer from very low external quantum efficiency due to the great blocking and shadowing of incident or radiative lights by opaque electrodes. To improve the external quantum efficiency, the method to avoid this so called current crowding problem, thereby obtaining high efficiency and uniform light emission from the device is to reduce the specific contact resistance of the very thin metal contact to p-GaN.
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