Enhanced performances of InGaN/GaN-based blue light-emitting diode with InGaN/AlInGaN superlattice electron blocking layer

A theoretical study of polar and semi/non-polar InGaN/GaN light-emitting diodes (LEDs) with different internal surface polarization charges, which can be grown on Si substrates, is conducted by using APSYS software. In comparison with polar structure LEDs, the semi-polar structure exhibits a higher concentration of electrons and holes and radiative recombination rate, and its reduced built-in polarization field weakens the extent of band bending which causes the shift of peak emission wavelength. So the efficiency droop of semi-polar InGaN/GaN LEDs declines obviously and the optical power is significantly improved. In comparison with non-polar structure LEDs, although the concentration of holes and electrons as well as the radiative recombination rate of the semi-polar structure are better in the last two quantum wells (QWs) approaching the p-GaN side, the uniformity of distribution of carriers and radiative recombination rate for the non-polar structure is better. So the theoretical analysis indicates that the removal of the internal polarization field in the MQWs active regions for non-polar structure LEDs contributes to the uniform distribution of electrons and holes, and decreases the electron leakage. Thus it enhances the radiative recombination rate, and further improves the IQEs and optical powers, and shows the best photoelectric properties among these three structures.

Section: Structure and Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of semi/non-polar InGaN/GaN light-emitting diodes grown on silicon substrates

Yu¹,

Zhang²,

Li³

et al. 2015

“…The current diffusion issue and its related current crowding effect (CCE) are important for the optoelectrical devices, such as laser diode (LD) and light emitting diodes (LEDs). [1][2][3] The theory of current spreading under a linear stripe top contact geometry has been reported by Thompson. [4] They claimed that the current density is inversely square dependent on the distance from the metal electrode edge.…”

Section: Introductionmentioning

confidence: 99%

Current diffusion and efficiency droop in vertical light emitting diodes*

Wan¹,

Li²,

Liu³

et al. 2019

Current diffusion is an old issue, nevertheless, the relationship between the current diffusion and the efficiency of light emitting diodes (LEDs) needs to be further quantitatively clarified. By incorporating current crowding effect (CCE) into the conventional ABC model, we have theoretically and directly correlated the current diffusion and the internal quantum efficiency (IQE), light extraction efficiency (LEE), and external quantum efficiency (EQE) droop of the lateral LEDs. However, questions still exist for the vertical LEDs (V-LEDs). Here firstly the current diffusion length L s(I) and L s(II) have been clarified. Based on this, the influence of CCE on the EQE, IQE, and LEE of V-LEDs were investigated. Specifically to our V-LEDs with moderate series resistivity, L s(III) was developed by combining L s(I) and L s(II), and the CCE effect on the performance of V-LEDs was investigated. The wall-plug efficiency (WPE) of V-LEDs ware investigated finally. Our works provide a deep understanding of the current diffusion status and the correlated efficiency droop in V-LEDs, thus would benefit the V-LEDs' chip design and further efficiency improvement.

“…[8][9][10][11] In order to enhance the internal quantum efficiency (IQE) as well as reduce efficiency droop, many researches focus on improving light output power and increasing radioactive recombination by increasing hole injection, strengthening carrier confinement in the quantum wells (QWs), alleviating electron leakage and weakening polarization electrostatic field in the active region. [12,13] All of those efforts lead to entering the mature period of visible light emission device technologies. Therefore, a new field-invisible light optoelectronic device with a shorter wavelength, known as an ultraviolet light-emitting diode (UV-LED), has gained researchers' close attention.…”

Section: Introductionmentioning

confidence: 99%

Performance improvement of AlGaN-based deep ultraviolet light-emitting diodes with double electron blocking layers

Zhang¹,

Sun²,

Li³

et al. 2016

The AlGaN-based deep ultraviolet light-emitting diodes (LED) with double electron blocking layers (d-EBLs) on both sides of the active region are investigated theoretically. They possess many excellent performances compared with the conventional structure with only a single electron blocking layer, such as a higher recombination rate, improved light output power and internal quantum efficiency (IQE). The reasons can be concluded as follows. On the one hand, the weakened electrostatic field within the quantum wells (QWs) enhances the electron–hole spatial overlap in QWs, and therefore increases the probability of radioactive recombination. On the other hand, the added n-AlGaN layer can not only prevent holes from overflowing into the n-side region but also act as another electron source, providing more electrons.