Influence of carrier screening and band filling effects on efficiency droop of InGaN light emitting diodes

Abstract

In this paper, the self-consistent solution of Schrödinger-Poisson equations was realized to estimate the radiative recombination coefficient and the lifetime of a single blue light InGaN/GaN quantum well (QW). The results revealed that the recombination rate was not in proportion to the total injected carriers, and thus the Bnp item was not an accurate method to analyze the recombination process. Carrier screening and band filling effects were also investigated, and an extended Shockley-Read-Hall coefficient A(kt) with a statistical weight factor due to the carrier distributions in real and phase space of the QW was proposed to estimate the total nonradative current loss including carrier nonradiative recombination, leakage and spillover to explain the efficiency droop behaviors. Without consideration of the Auger recombination, the blue shift of the electroluminescence spectrum, light output power and efficiency droop curves as a function of injected current were all investigated and compared with the experimental data of a high brightness blue light InGaN/GaN multiple QWs light emitting diode to confirm the reliability of our theoretical hypothesis.

Direct Measurement of Auger Electrons Emitted from a Semiconductor Light-Emitting Diode under Electrical Injection: Identification of the Dominant Mechanism for Efficiency Droop

“…However, the interpretation of the droop phenomenon remains highly controversial, in spite of its importance and many studies. Many proposed mechanisms rely on the enhanced nonradiative (NR) recombination at point defects in either quantum barriers or surrounding majority carrier regions when carriers are no longer localized in the high radiative recombination efficiency regions of quantum wells (QWs): carrier overflow from the QWs into regions of efficient NR recombination [4,5] in particular due to saturation of localized states in the QWs [6]; loss of current injection efficiency [5]; density-activated defect recombination [7]; insufficient hole injection efficiency leading to electron leakage [8]. Auger recombination in the QW is however a somewhat favored mechanism [3], with possibly an early onset induced by the reduction in active volume due to current crowding [9] or by carrier localization [10,11].…”

On the Effect of Step-Doped Quantum Barriers in InGaN/GaN Light Emitting Diodes

“…In this work, we study both numerically and experimentally on the step-doping of the quantum barriers with Si, which could effectively screen the QCSE through the ionized dopants by properly designing the doped thickness and position in the quantum barriers. This provides additional degree of freedom of designing thicker quantum wells to avoid carrier high energy state filling, relieving the efficiency droop in c-plane LEDs [36]. The proposed step-doped quantum barriers could reduce hole blocking effect, promote electron injection, quench polarization fields and enhance electron-hole wave function overlap within the quantum wells.…”

Strong carrier localization and diminished quantum-confined Stark effect in ultra-thin high-indium-content InGaN quantum wells with violet light emission

“…Generally, as total injected carrier density increases, the main MQW emission peak energy shifts to higher energy for conventional low-In-content InGaN/GaN MQWs due to the carrier screening and band filling effects. 12,13 However, an apparent peak shift in the CL spectra for sample A with increasing electron-beam current was not observed. To further investigate this behavior, the PL emission peak energy for sample A was also investigated with varying excitation power densities over three orders of magnitude at 15 K, as indicated in Fig.…”