Anelasticity of GaN Epitaxial Layer in GaN LED

In this work, the anelasticity of theGaNlayer in theGaNlight-emitting-diode device was studied.The present results show that the forward-voltage ofGaNLED increases with time, as theGaNlight-emittingdiodewas maintained at a constant temperature of 100 °C.Wefound that the increase of the forwardvoltagewith time attributes to the delay-response of the piezoelectric fields (internal electrical fields in GaNLEDdevice).And, the delay-response of the internal electricalfields with time is caused by the anelasticity (time-dependent strain) of theGaNlayer. Therefore, using the correlation of strainpiezoelectric-forward voltage, a plot of thermal strain of theGaNlayer against time can be obtained by measuring the forward-voltage of the studiedGaNLEDagainst time.With the curves of the thermal strain ofGaNepi-layers versus time, the anelasticity of theGaNcompound can be studied. The key anelasticity parameter, characteristic relaxation time, of theGaNis defined to be 2623.76 min in thiswork.