Effect of lattice‐matched InAlGaN electron‐blocking layer on hole transport and distribution in InGaN/GaN multiple quantum wells of visible light‐emitting diodes

Abstract

We report on the influence of lattice‐matched InAlGaN quaternary electron‐blocking layer (Q‐EBL) on hole transport and distribution in InGaN/GaN multiple quantum wells (MQWs) of visible light‐emitting diodes (LEDs). Triple‐wavelength (TW)‐emitting active region was introduced to deduce carrier transport and distribution from emission intensities of different QWs in TW‐LEDs. The electro‐optical characteristics of TW‐LEDs were compared with respect to the Q‐EBL and silicon doping in a selected QW barrier. In addition, the efficiency droop characteristics of TW‐LEDs according to existence of the Q‐EBL were also investigated. The results show that holes were preferentially injected into a QW adjacent to a p‐type layer in the TW‐LED without the Q‐EBL, while enhanced hole transport to lower QWs closed to an n‐type layer and following uniform distribution were observed in the TW‐LED with the Q‐EBL. The modified kinetic energy of holes overcoming the Q‐EBL is responsible for the improved hole transport and changes in the carrier capturing efficiency of each different QW, resulting in the improved peak efficiency and the efficiency droop of TW‐LEDs.

Electroluminescence from the InGaN/GaN Superlattices Interlayer of Yellow LEDs with Large V-Pits Grown on Si (111)

“…Hence, the hole must be sped up for compensation and thus be entitled to higher kinetic energy to achieve a certain current. Then, the increased kinetic energy of holes could reduce the opportunity of them being captured by QWs and could drive more holes to transport further, [24,25] helping the emission of P3. This also explains why the intensity of P3 rises faster and can exceed P2 with decreasing temperature or increasing current.…”

Di-Chromatic InGaN Based Color Tuneable Monolithic LED with High Color Rendering Index

“…We attribute this to the non-uniform distribution of injected holes. Primarily, due to their lower mobility, higher effective mass, and poor transport among the MQW structure [23] holes will radiatively recombine in the QW closer to the p-side. However, with further increase in current, more holes travel through the barrier layer and are available for recombination in blue QWs.…”

“…In MQW structures, non-uniform hole redistribution leading to dominant EL intensity from the QW at lower currents has been observed. Methods such as quaternary electron blocking layer [23], InGaN barrier layers [24] and varying thickness of the barrier layers [25] have been proposed to achieve better hole injection and transport among the QWs. On further increasing the current up to 100 mA, the emission from green QW is clamped and the radiative recombination in the blue QW is enhanced.…”

Temperature Dependence of Electron Leakage Current in InGaN Blue Light-Emitting Diode Structures

“…In typical InGaN blue LED structures, an electron-blocking layer (EBL) with a large energy bandgap material is inserted between MQWs and a p-GaN layer to suppress the electron leakage. There have been lots of studies on the design of EBL structures to decrease electron leakage current through effective blocking of electrons or improvement in hole injection [ 24 , 25 , 26 , 27 , 28 , 29 ]. One may expect that the electron leakage current increases with increasing temperature because thermionic emission generally increases with temperature [ 30 , 31 ].…”