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In this study, the influence of multiple interruptions with trimethylindium (TMIn)-treatment in InGaN/GaN multiple quantum wells (MQWs) on green light-emitting diode (LED) is investigated. A comparison of conventional LEDs with the one fabricated with our method shows that the latter has better optical properties. Photoluminescence (PL) full-width at half maximum (FWHM) is reduced, light output power is much higher and the blue shift of electroluminescence (EL) dominant wavelength becomes smaller with current increasing. These improvements should be attributed to the reduced interface roughness of MQW and more uniformity of indium distribution in MQWs by the interruptions with TMIn-treatment.

The energy band structures, density of states, and optical properties of IIIA-doped wurtzite Mg0.25Zn0.75O (IIIA = Al, Ga, In) are investigated by a first-principles method based on the density functional theory. The calculated results show that the optical bandgaps of Mg0.25Zn0.75O:IIIA are larger than those of Mg0.25Zn0.75O because of the Burstein—Moss effect and the bandgap renormalization effect. The electron effective mass values of Mg0.25Zn0.75O:IIIA are heavier than those of Mg0.25Zn0.75O, which is in agreement with the previous experimental result. The formation energies of MgZnO:Al and MgZnO:Ga are smaller than that of MgZnO:In, while their optical bandgaps are larger, so MgZnO:Al and MgZnO:Ga are suitable to be fabricated and used as transparent conductive oxide films in the ultra-violet (UV) and deep UV optoelectronic devices.

The characteristics of a blue light-emitting diode (LED) with a p-InAlGaN hole injection layer (HIL) is analyzed numerically. The simulation results indicate that the newly designed structure presents 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-InAlGaN 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.

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.

The efficiency enhancement of an InGaN light-emitting diode (LED) with an AlGaN/InGaN superlattice (SL) electron-blocking layer (EBL) is studied numerically, which involves the light-current performance curve, internal quantum efficiency electrostatic field band wavefunction, energy band diagram carrier concentration, electron current density, and radiative recombination rate. The simulation results indicate that the LED with an AlGaN/InGaN SL EBL has better optical performance than the LED with a conventional rectangular AlGaN EBL or a normal AlGaN/GaN SL EBL because of the appropriately modified energy band diagram, which is favorable for the injection of holes and confinement of electrons. Additionally, the efficiency droop of the LED with an AlGaN/InGaN SL EBL is markedly improved by reducing the polarization field in the active region.

Blue InGaN light-emitting diodes (LEDs) with a conventional electron blocking layer (EBL), a common n-AlGaN hole blocking layer (HBL), and an n-AlGaN HBL with gradual Al composition are investigated numerically, which involves analyses of the carrier concentration in the active region, energy band diagram, electrostatic field, and internal quantum efficiency (IQE). The results indicate that LEDs with an n-AlGaN HBL with gradual Al composition exhibit better hole injection efficiency, lower electron leakage, and a smaller electrostatic field in the active region than LEDs with a conventional p-AlGaN EBL or a common n-AlGaN HBL. Meanwhile, the efficiency droop is alleviated when an n-AlGaN HBL with gradual Al composition is used.

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.

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.

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.

InGaN based light-emitting diodes (LEDs) with dip-shaped quantum wells and conventional rectangular quantum wells are numerically investigated by using the APSYS simulation software. It is found that the structure with dip-shaped quantum wells shows improved light output power, lower current leakage and less efficiency droop. Based on numerical simulation and analysis, these improvements on the electrical and the optical characteristics are attributed mainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells (MQWs).