Improvement of device performances, including electrostatic discharge characteristics, of InGaN/GaN light-emitting diodes by using a Si-doped graded superlattice

We report the influences of a Si-doped graded-superlattice (SiGSL) on the structural, optical, and electrical properties of InGaN/GaN light-emitting diodes (LEDs). For comparison, LEDs fabricated on an undoped graded superlattice (unGSL-LED) and conventional LEDs without the superlattice (C-LED) were prepared. The dependences of the carrier behaviors on the surface inhomogeneity and the defect/dislocation distribution were investigated by using fluorescence microscopy images, wherein the dark features corresponding to the defects/threading dislocations for the unGSL-LED and the SiGSL-LED were significantly reduced compared to that for the C-LED. The photoluminescence intensities of the unGSL-LED and the SiGSL-LED were 1.15 and 1.24 times stronger than that of the C-LED, respectively. The output powers of the unGSL-LED and the SiGSL-LED at an injection current of 20 mA were measured to be 1.32 and 1.41 times higher than that of the C-LED, respectively. Moreover, the electrostatic discharge characteristics of the LED sample using the SiGSL structure were drastically improved.