High quality epitaxial growth and uniform current spreading are essential to III-nitride light emitting diodes (LEDs) for
superior wall-plug efficiency and reliability. An analysis method of current spreading based on 3-dimensional circuit
modeling is introduced. We have investigated influences of the current spreading in the lateral-electrode type blue LEDs
of 320 × 320 μm<sup>2</sup> size theoretically and experimentally. It is known that the current spreading can be greatly reduced by careful design of electrode pattern. Uniform current spreading is very important to improve electrical and optical
characteristics such as series resistance, efficiency droop, leakage current with operational time leakage current, and
electrostatic discharge (ESD) voltage. A method improving ESD voltage is presented by inserting floating metal near the n-electrode. About 4 times larger ESD voltages are experimentally measured at LEDs with floating metal compared to conventional LEDs without one. The internal quantum efficiency (IQE) is the most important factor affecting overall LED performances. A measurement method of the IQE measurable just at room temperature is proposed and demonstrated. The method utilizes both the time responses of the time-resolved photoluminescence (TRPL) as a function of the excitation femtosecond laser pumping power and their theoretical analysis based on the carrier rate equation.
In this study, effects of n-electrode patterns to the current spreading in the active region were analyzed on the blue
vertical light emitting diode (VLED) with GaN/InGaN multi quantum well (MQW). Several n-electrode patterns of the
VLED are designed, analyzed qualitatively, and investigated its effect to current spreading in the active region. A 3-dimensinal circuit model whose parameters are experimentally extracted from an actual VLED chip is adopted for the
quantitative analysis of current spreading. The n-electrode patterns are modeled and simulated by simple electrical
circuits in order to find the current distribution and current-voltage characteristics of devices. Based on theoretical
analysis results, blue VLEDs with different n-electrode patterns were fabricated and a series of measurements were
carried out. Analytic and experimental results for different n-electrode pattern showed quite similar tendencies. Finally,
we proposed some design methodologies for improved current spreading.