Dual-blue Wavelength Light-emitting Diodes Based on Varied GaN Barrier Thickness

Due to low color rendering index of white light-emitting diodes based on packing of single-blue wavelength chip and Y3Al5O12∶Ce3+yellow phosphors,using dual-blue wavelength chip,Y3Al5O12∶Ce3+yellow phoshpor is proposed to realize high color rendering index white emission,and feasibility of the method is analyzed.Dual-blue wavelength light-emitting diodes based on two pairs of In0.18Ga0.82N/GaN quantum-well and two pairs of In0.12Ga0.88N/GaN quantum-well structure were grown sequentially on the same sapphire substrate by metal-organic chemical vapor deposition.Optoelectronic properties of dual-wavelength light-emitting diodes with different GaN barrier thicknesses were also studied.The experimental results indicate that efficient dual-blue-wavelength emission and higher luminescent efficiency are realized from lightemitting diodes by reducing GaN barrier thickness from n-GaN to p-GaN.The a.c.impedance spectroscopy can be explained in terms of the equivalent series circuit model of a set of parallel resistor-capacitor RpCpand a resistor Rsfor the dual-blue wavelength light-emitting diodes.Varied GaN barrier thickness can tune parallel resistor and capacitor while it has no effect on series resistor.In addition,Y3Al5O12∶Ce3+phosphor-converted white light emission with high color rendering index is achieved by use of dual-blue emitting active regions from reducing barrier thickness.