Analysis of nonradiative recombination mechanisms and their impacts on the device performance of InGaN/GaN light-emitting diodes

Abstract

We investigate the nonradiative recombination mechanisms of two conventional InGaN/GaN-based blue light-emitting diodes with different threading dislocation densities (TDDs). The current–voltage, the ideality factor, and the slope of the light-versus-current curve on log scales are analyzed to distinguish the dominant nonradiative recombination mechanisms at room temperature. Through the analysis, we infer the dominant nonradiative recombination mechanisms to be the Shockley–Read–Hall process for the sample with a low TDD (∼1 × 108 cm−2) and the defect-assisted tunneling for the sample with a high TDD (∼1 × 109 cm−2). For more detailed analysis of the nonradiative recombination mechanisms and their impacts on the device performance, we execute the temperature-dependent photovoltage and temperature-dependent electroluminescence efficiency experiments. The sample with a low TDD is found to be more prone to the carrier spill-over at cryogenic temperatures due to the deactivation of point defects, while the sample with a high TDD is more robust to the operation at cryogenic temperatures owing to the relative insensitiveness of the defect-assisted tunneling to temperature.

Enhanced Radiative Recombination Rate by Local Potential Fluctuation in InGaN/AlGaN Near-Ultraviolet Light-Emitting Diodes

“…Figure 4b shows the S characteristics of the samples, where the S values, obtained from the differential slope of log L vs. log I, indicate the dominant carrier-recombination mechanism at a given applied bias. The values of S > 2, 2, 1, and < 1 represent tunneling current, SRH recombination via defects, radiative recombination, and carrier leakage through overflow, respectively [36]. At a low current (10 mA), the sample's S value decreased (see Table 1) due to the decrease in point defects, which is consistent with nmin and Figure 3.…”

Characterization of semi-polar (20$$\overline{2}$$1) InGaN microLEDs

“…The LEDs created on these two blue epitaxial structures had four different sizes: 100 μm × 100 μm, 75 μm × 75 μm, 25 μm × 25 μm, and 10 μm × 10 μm, which were all used to evaluate the influence of chip size and optical characteristics. In this study, the above LEDs were defined as LED(100), LED(75), LED (25), and LED (10), respectively. Four different chip sizes (LED(100), LED(75), LED (25), and LED(10)) of blue LEDs with CPSS and SPSS orientations were fabricated.…”

“…In Eq. ( 1 ), q is the elementary charge, k is the Boltzmann constant, and T is the absolute temperature 7 – 9 . The ideality factor gradually decreased from 3.75 to 2.66 as the chip size increased from 10 to 100 μm for the CPSS LEDs.…”

“…Correspondingly, the SPSS LED consisted of a 4 μm thick n-type GaN, a 50 nm thick active layer, a 300 nm thick p-type GaN, and a 200 nm thick ITO layer. The LEDs created on these two blue epitaxial structures had four different sizes: LED(100), LED(75), LED (25), and LED (10), which were all used to evaluate the influence of chip size and optical characteristics. www.nature.com/scientificreports/ Figure 8 shows the complete process flow chart for the μ-LED fabrication.…”

Optoelectronic Performance Variations in InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes: Effects of Potential Fluctuation

“…The minimum IFs of samples #1, #2, and #3 are 1.52, 1.47, and 1.45, respectively, as shown in the inset of Figure 4 b, and the current at the minimum IFs are 0.20, 0.10, and 0.09 mA for samples #1, #2, and #3, respectively. The band-to-band radiative recombination current has an IF of 1 [ 46 ], the nonradiative current associated with the SRH recombination via defects has an IF of 2, and the nonradiative recombination current from the defect-assisted tunneling or the surface recombination has an IF > 2 [ 47 ]. The decrease in the IF close to 1 indicates the rapid dominance of the radiative recombination rate over the nonradiative recombination rate.…”