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|Type of Document
||Study of GaN LED current spreading and chip fabrication|
|Date of Defense
Pattern of Electrode
||In this thesis, we design electrode shape of light emitter diode (LED) to help the current diffusing uniformly. The purpose of the uniform current is to avoid the waste heat from the devices and enhance the efficiency of active region. The LED samples adopted in this study are GaN base materials grown on sapphire. The P-N electrodes must be processed on the same side since the poor conductivity of sapphire. The same side P-N electrode will results in current crowding phenomena. We design special electrode shapes to make the current diffuse uniformly and reduce the current crowding phenomena. |
First, we use COMSOL simulation software to simulate the current spreading between the electrodes. We adopt the same parameters from the reference papers to confirm the reliabilities of the simulation. Then we simulate several electrode shapes with highly uniform current spreading.
Second, we use the simulation results to fabricate electrode on chips. The first set is LED without transparent conductive layer. This set is to confirm whether the fabrication processes is feasible and adjust the simulation parameters at the same time.
The second set is LED with transparent conductive layer. The experimental emission intensity has deviation from the simulation results. We deduce the emission intensities
from smaller LED chip size will have great influence on illumination surface. The third set is electrodes fabricated on large size LED chip. The electrode patterns successfully enhance the uniformity of current spreading, and enhance the output light
intensity of 21%. The current density distribution trend from simulation is matched with the illumination intensities.
||Min-Hsiung Shih - chair|
Chien-Chung Lin - co-chair
Jau-Sheng Wang - co-chair
Jui-Yang Feng - co-chair
Tsong-Sheng Lay - advisor
Indicate in-campus at 99 year and off-campus access at 99 year.|
|Date of Submission