Efficiency Improvement Using Thickness-Chirped Barriers in Blue InGaN Multiple Quantum Wells Light Emitting Diodes

Abstract

The advantages of blue InGaN light-emitting diodes (LEDs) with thicknesschirped barriers in the active region have been investigated by using the Crosslight APSYS programs. The results show that the output power of the proposed LED is increased 80% and the efficiency droop is decreased from 59% in conventional LED to 28% at the current of 250 mA. Based on the analysis of electrical and optical characteristics, these improvements are mainly attributed to the change of electrostatic field in the active region by using thickness-chirped barriers. In the even-numbered barriers, the fields are increased, which gets rid of more seriously bended valence band and results in decreased barrier heights for hole transport in the active region. Furthermore, the direction of electrostatic field in the last barrier is reversed to along the drift direction of holes, which not only can lead to upbended conduction band to rise the barrier height for electron escape but also can accelerate holes to increase the hole injection current. As a result, electrons blocking and holes injection are enhanced, and in turn, the performance of the proposed LED is improved.

Enhanced Performance of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes with Chirped Superlattice Electron Deceleration Layer

“…To illuminate the mechanism of performance enhancement of DUV LEDs, the band diagram, optical properties, and carrier transport characteristics of this structure were simulated by solving the Schrödinger equation, Poisson’s equation, the carrier transport equations, and the current continuity equation self-consistently by Crosslight APSYS (Advance Physical Model of Semiconductor Devices) programs [28]. The Shockley-Read-Hall (SRH) recombination time is set to be 1.5 ns for all layers except the p-type inserted layer as 1 ns because the SRH lifetime is dependent upon the doping level [29].…”

Enhanced Performance of InGaN‐Based Blue LEDs Using an AlGaN/InGaN Super‐Lattice Last Quantum Barrier

“…Earlier reports have proposed approaches to relieve the thermionic electron escape process. Tian et al proposed that a novel structure with thickness‐chirped quantum barriers in the active region, that it can improve the efficiency barrier of EBL and enhance the injection of hole . Also in the quantum well, Yen et al focused on the design of last quantum barrier (LQB), and by thinning the thickness of LQB, the efficiency droop under the condition of high injection current level can be reduced .…”

Performance enhancement of blue light-emitting diodes by using special designed n and p-type doped barriers

“…Furthermore, thinner QBs possess weaker QCSE and are proved effective in homogenizing the hole distribution, but the electrons may spill over the thin QBs without recombining with holes [18]. LEDs with thickness-varied QBs [18,19] show superior optical performance because of the improved uniformity in the hole distribution and thus, radiative recombination rates across the active region.…”