Characterization of chip size effect on thermal-optical properties of GaN-based light emitting diodes

The effect of chip size on the thermal-optical properties of GaN-based light emitting diodes was investigated. An increase in chip size was associated with a decrease of total series resistance due to enhancement of current spreading area. Consequently, the junction temperature linearly increased with an increase of the driving current, and the increase rate was slower for lager chip size. Moreover, we found out that the driving current and chip size affect the dominant emission wavelength shift that was understood to be a competition between blue shift behaviors of piezoelectricity-induced quantum confined stark effect and red shift behavior of self-heating effect. Thus, the operating current for color stabilization was increased with increasing chip size such as 80mA, 140mA and 160mA for 350×350μm2, 600×600μm2 and 1000×1000μm2 chip sizes, respectively. Herein, the operating current for color stabilization was determined at the driving current, where blue shift of piezoelectricity-induced quantum confined stark effect became in balance with the temperature induced band gap shrinkage resulted from self-heating effect.