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Three kinds of InGaN/GaN multiple-quantum-well light-emitting diode with different electron-blocking layers (EBLs) have been investigated numerically. The energy band diagrams, light-current curves, voltage-current curves, electrostatic fields, carrier concentrations in the quantum wells, electron current densities, radiative recombination rates in active region, and internal quantum efficiency (IQE) are reported. The results show that, when the conventional AlGaN EBL is replaced by a p-AlGaN/InGaN superlattice EBL or graded p-AlGaN/InGaN superlattice EBL, respectively, the light output power at 200 mA can be increased by 46.0% and 52.8%, the turn-on voltage can be decreased from 3.2 V to 3.0 V, the IQE can be increased by 45.6% and 53.8% at 200 mA, and the efficiency droop can be reduced from 31.2% to 21.6%. These improvements are mainly attributed to the properly modified energy band structures which favor carrier injection. [ABSTRACT FROM AUTHOR]

In this study, a new design of quantum barriers has been investigated numerically with the purpose of improving the optical performance of blue InGaN light-emitting diodes (LEDs). Through analysis of energy band diagrams, carrier concentrations, carrier current densities, Auger recombination rates, and radiative recombination rates, we obtain simulation results showing that the proposed structure with a mix of AlGaN and InGaN quantum barriers can significantly improve the light output power and internal quantum efficiency (IQE), being mainly attributed to successful enhancement of the hole injection efficiency and suppression of the electron leakage current. Moreover, the efficiency droop of the LEDs is markedly improved by using the newly designed structure. [ABSTRACT FROM AUTHOR]

In this study, three kinds of electron-blocking layer (EBL) in blue InGaN light-emitting diodes (LEDs) are investigated numerically. They are conventional AlGaN EBL, AlInGaN EBL and gradual Al and In composition p-AlInGaN EBL. Through the analysis of the output power, internal quantum efficiency, turn-on voltage, energy band diagrams, carrier current densities and radiative recombination rates, we have got the simulation results that the LED with gradual Al and In composition p-AlInGaN EBL exhibits a higher output power, a lower electron leakage, a better hole injection efficiency and a more peaceable efficiency droop than the LED with a conventional AlGaN EBL or with a AlInGaN EBL. [ABSTRACT FROM AUTHOR]

In this study, a new design on last quantum barrier (LQB) is investigated numerically with the purpose of improving the optical performance of InGaN light-emitting diodes (LEDs). Through the analysis of the energy band diagrams, electrostatic fields, carrier concentrations, carrier current densities, and radiative recombination rates, we have got the simulation results that the proposed undoped-InGaN/AlInGaN superlattice (SL) LQB can significantly improve the output power and internal quantum efficiency, which is mainly attributed to the successful improvement in hole injection efficiency and suppression of electron current leakage. Moreover, the efficiency droop of the LEDs is improved slightly by using u-InGaN/AlInGaN SL as last barrier. [ABSTRACT FROM AUTHOR]

The characteristics of blue InGaN light-emitting diodes (LEDs) with InGaN barriers and dip-shaped last barrier are investigated numerically. The simulation results show that the newly designed LEDs have a better performance over the conventional InGaN/GaN and InGaN/InGaN counterparts attributed to the enhancement of carriers confinement induced by the improved potential barrier height for electrons and holes, and the amelioration of electron–hole spatial overlap caused by the reduced polarization effect between the well and barrier. In addition, the efficiency droop and the radiative recombination rate are markedly improved by employing the LEDs with InGaN barriers and dip-shaped last barrier. [ABSTRACT FROM PUBLISHER]

The blue InGaN light-emitting diodes (LEDs), employing a lattice-compensated p-AlGaN/InGaN superlattice (SL) interlayer to link the last quantum barrier and electron blocking layer (EBL), are proposed and investigated numerically. The simulation results indicate that the newly designed LEDs have better hole injection efficiency, lower electron leakage, and smaller electrostatic fields in the active region over the conventional LEDs mainly attributed to the mitigated polarization-induced downward band bending. Furthermore, the markedly improved output power and efficiency droop are also suggested when the conventional LEDs corresponding to experiment data are replaced by the newly designed LEDs. [ABSTRACT FROM AUTHOR]

The characteristics of a blue light-emitting diode (LED) with an AlInN/GaN superlattice (SL) electron-blocking layer (EBL) are analyzed numerically. The carrier concentrations in the quantum wells, energy band diagrams, electrostatic fields, and internal quantum efficiency are investigated. The results suggest that the LED with an AlInN/GaN SL EBL has better hole injection efficiency, lower electron leakage, and smaller electrostatic fields in the active region than the LED with a conventional rectangular AlGaN EBL or a AlGaN/ GaN SL EBL. The results also indicate that the efficiency droop is markedly improved when an AlInN/GaN SL EBL is used. [ABSTRACT FROM AUTHOR]

InGaN-based light-emitting diodes with p-GaN and p-AlGaN hole injection layers are numerically studied using the APSYS simulation software. The simulation results indicate that light-emitting diodes with p-AlGaN hole injection layers show superior optical and electrical performance, such as an increase in light output power, a reduction in current leakage and alleviation of efficiency droop. These improvements can be attributed to the p-AlGaN serving as hole injection layers, which can alleviate the band bending induced by the polarization field, thereby improving both the hole injection efficiency and the electron blocking efficiency. [ABSTRACT FROM AUTHOR]

P-AlGaN/P-GaN superlattices are investigated in blue InGaN light-emitting diodes as electron blocking layers. The simulation results show that efficiency droop is markedly improved due to two reasons: (i) enhanced hole concentration and hole carrier transport efficiency in AlGaN/GaN superlattices, and (ii) enhanced blocking of electron overflow between multiple quantum-wells and AlGaN/GaN superlattices. [ABSTRACT FROM AUTHOR]

The performance of InGaN blue light-emitting diodes (LEDs) with different kinds of electron-blocking layers is investigated numerically. We compare the simulated emission spectra, electron and hole concentrations, energy band diagrams, electrostatic fields, and internal quantum efficiencies of the LEDs. The LED using AlGaN with gradually increasing Al content from 0% to 20% as the electron-blocking layer (EBL) has a strong spectrum intensity, mitigates efficiency droop, and possesses higher output power compared with the LEDs with the other three types of EBLs. These advantages could be because of the lower electron leakage current and more effective hole injection. The optical performance of the specifically designed LED is also improved in the case of large injection current. [ABSTRACT FROM AUTHOR]

Optical properties of GaN-based light-emitting diodes (LEDs) are studied numerically by using AlGaN and InAlN electron-blocking layers (EBLs). Through the simulations of emission spectra, carrier concentration distribution, energy band, electrostatic field, internal quantum efficiency and output power, the results show that the LEDs with design of the InAlN EBL structure have a better performance over the original LEDs using an AlGaN EBL. The spectrum intensity and output power are enhanced significantly, and the efficiency droop of internal quantum efficiency is improved effectively with this design of InAlN EBL structure. It is proved that the strengths of carrier confinement and electron leakage current play a critical role in the performance of luminescence in LEDs. [ABSTRACT FROM AUTHOR]

The characteristics of blue InGaN light-emitting diodes with AlGaN barriers of different step-like growth range Al composition and gradually increasing Al composition are investigated numerically. The simulation results indicate that the enhanced electron confinement and hole injection efficiency are mainly attributed to the mitigated downward band bending of the last barrier induced by polarization field, and the improved carrier distribution is owing to the increasing blocking for electrons as well as the decreasing blocking for holes. What's more, the output power, the distribution and rate of radiative recombination and the efficiency droop are markedly improved. [ABSTRACT FROM AUTHOR]

Abstract: The advantages of GaN based light-emitting diodes (LEDs) with strain-compensated p-AlGaN/InGaN superlattice (SL) last quantum barrier (LQB) are investigated numerically. The simulation results indicate that the output power and internal quantum efficiency have been improved significantly by replacing the last barrier of the conventional u-GaN and p-GaN with p-AlGaN/InGaN SL. These improvements are mainly attributed to the improvement of electron confinement and hole injection efficiency caused by mitigating the polarization-induced band bending of last barrier with the new designed structure. Moreover, the efficiency droop of the LEDs is markedly improved by using p-AlGaN/InGaN SL as last barrier. [Copyright &y& Elsevier]