Impact of superlinear defect-related recombination on LED performance at low injection

Abstract

We investigate the temperature and injection dependence of the electroluminescence from an InGaN/GaN LED to characterize the defect-related recombination mechanism in this system. In contrast to the standard ABC recombination model, we show that the defect-related recombination rate varies superlinearly with carrier density. The elevated loss rate with injection indicates that defect states are less detrimental at low injection, only becoming available for occupation via carrier delocalization or more dynamic Shockley-Read-Hall statistics. This characteristic alleviates defect-related losses by making the radiative mechanism more competitive such that high dislocation density devices can perform better at low injection.

Impact of Localization on the Optical Properties of InGaN-Based Red Light-Emitting Diodes Grown on a Silicon Substrate

“…The I – V curves of InGaN-based red LEDs at temperatures ranging from 20 to 300 K are plotted on a semilogarithmic scale in Figure a, and the leakage current decreases from the nA level at 300 K to the subnanoampere level at 20 K. Here, Mott’s law is employed to demonstrate the temperature dependence of the tunneling current, which can be expressed as I false( T false) ∝ exp [ prefix− true( T 0 T true) 1 / 4 ] where, I ( T ) denotes the current and T 0 denotes the characteristic temperature. The experimental temperature-current relationships of the InGaN-based red LEDs at forward biases of 1.5 and 1.8 V are shown in Figure b . These two voltages are lower than the threshold voltage of the InGaN-based red LEDs, and the injected carriers primarily participate in nonradiative recombination.…”

“…The experimental temperaturecurrent relationships of the InGaN-based red LEDs at forward biases of 1.5 and 1.8 V are shown in Figure 4b. 24 These two voltages are lower than the threshold voltage of the InGaNbased red LEDs, and the injected carriers primarily participate in nonradiative recombination. When the temperature exceeds 180 K, a reasonably fitted nonradiative current of thermally activated Shockley−Read−Hall (SRH) recombination can be obtained.…”

“…These two voltages are lower than the threshold voltage of the InGaN-based red LEDs, and the injected carriers primarily participate in nonradiative recombination. When the temperature exceeds 180 K, a reasonably fitted nonradiative current of thermally activated Shockley–Read–Hall (SRH) recombination can be obtained . However, when the temperature is lower than 100 K, the results fit well with Mott’s law, suggesting that the tunneling current would dominate the leakage current, and the contribution of the tunneling current would lead to the efficiency degradation at low temperatures …”

Kinetic Monte Carlo simulations of the dynamics of a coupled system of free and localized carriers in AlGaN

“…The PL efficiency dependences on excitation power density generally exhibit efficiency droop, and are used to evaluate the contribution of Auger recombination [31,33], which is commonly accepted as the main origin of the efficiency droop in InGaN materials [42,43], and has been suggested to be important also in AlGaN [33]. Nevertheless, the Auger processes have also been shown to be affected by carrier localization [5,6,34], while recently, the importance of carrier localization to efficiency droop has reemerged [30,44,45]. This situation motivated us for an attempt to simulate the carrier dynamics in AlGaN by properly describing the influence of carrier localization and without the involvement of the Auger processes.…”

“…The initial increase of PL efficiency is typically attributed to several effects: the saturation of NRCs, the increasing role of bimolecular radiative recombination due to filling of localized states, and the screening of built-in electric field in QWs [11,41,45]. Likewise, the efficiency droop is also assigned to several competing mechanisms with Auger recombination and carrier delocalization being the most important [4, 7-11, 14, 31, 33, 41, 42, 44].…”