Fabrication and characterization of GaN-based blue light-emitting diodes

Abstract

GaN homojunction and InGaN/GaN single quantum well (SQW) light-emitting diodes (LEDs) were fabricated and characterized. The blue LED has a typical operating voltage of 3.6 V at 20 mS. Temperature dependence of the emission characteristics of the GaN-based LEDs was studied from 25 degrees C to 130 degrees C. The emission intensity of the InGaN/GaN SQW LED decays exponentially with the increase of temperature. The temperature coefficient Lc is 2.5 X 10-2/degrees C. The emission wavelength of the InGaN/GaN SQW LED was found to be relatively independent of the LED operation temperature while the UV emission of the GaN homojunction LED has a red-shift with the increase of temperature. The temperature coefficient (alpha) of the bandgap energy of Si-doped n-type GaN derived from the EL measurement is 8.5 X 10-4/K. The low temperature coefficient of emission wavelength of the InGaN/GaN SQW LED indicates that the recombination processes involves localized states. The localized states are attributed to excitons localized at the potential minima in the quantum well due to In content fluctuation.