Efficient Carrier Injection, Transport, Relaxation, and Recombination Associated with a Stronger Carrier Localization and a Low Polarization Effect of Nonpolar m-plane InGaN/GaN Light-Emitting Diodes

Abstract

Based on time-resolved electroluminescence (TREL) measurement, more efficient carrier injection, transport, relaxation, and recombination associated with a stronger carrier localization and a low polarization effect in a nonpolar m-plane InGaN/GaN light emitting diode (m-LED), compared with those in a polar c-LED, are reported. With a higher applied voltage in the c-LED, decreasing response time and rising time improve device performance, but a longer recombination time degrades luminescence efficiency. By using an m-LED with a stronger carrier localization and a low polarization effect, shorter response, rising, and recombination times provide more efficient carrier injection, transport, relaxation, and recombination. These advantages can be realized for high-power and high-speed flash LEDs. In addition, with a weaker carrier localization and a polarization effect in the c-LED, the slower radiative and faster nonradiative decay rates at a larger applied voltage result in the slower total decay rate and the lower luminescence efficiency. For the m-LED at a higher applied voltage, a slow decreasing nonradiative decay rate is beneficial to device performance, while the more slowly decreasing and overall faster radiative decay rate of the m-LED than that of the c-LED demonstrates that a stronger carrier localization and a reduced polarization effect are efficient for carrier recombination. The resulting recombination dynamics are correlated with the device characteristics and performance of the c- and m-LEDs.

Optimization of a triazine-based acceptor (CN-T2T) as the electron transport layer for highly efficient near-infrared perovskite light-emitting diodes

“…The injection, transport, and accumulation of charge carriers under varying applied voltages in the NIR PeLEDs were analyzed by the C − V characteristics of the devices. 38–40 For convenience, we chose three distinct devices to analyze the C – V characteristics at a fixed frequency of 1 KHz in the dark condition, as shown in Fig. 3.…”

Modulation of the carrier balance of lead-halide perovskite nanocrystals by polyelectrolyte hole transport layers for near-infrared light-emitting diodes

“…We observed a continuous increase in capacitance at moderate applied voltages (second regime), indicating suppression of depletion regions due to charge injection and accumulation. The 1MA-based NIR PeLEDs, in particular, rises faster than the other three devices, which is most likely due to more and more carriers being injected in the device, and a higher number of injected carriers leads to a faster rise rate [ 56 , 57 , 58 ]. Because electron injection in NIR PeLEDs uses the same device structure Liq/CN-T2T/Liq/Al, the faster rise of the 1MA device curve can only be explained by enhanced hole injection that resulted in balanced charge injection into EML.…”

Enhancing carrier transport and carrier capture with a good current spreading characteristic via graphene transparent conductive electrodes in InGaN/GaN multiple-quantum-well light emitting diodes

“…The overall resolution of TREL system is less than 2 ns. The detailed measurement was described in our previous study 18,19 .…”

“…Although device performance of GaN-based LEDs with graphene transparent conductive electrodes has been shown to be improved, these measurements cannot quantitatively describe carrier dynamic behaviors. Time-resolved electroluminescence (TREL) measurement under electrical fast pulse excitation is a power tool to explore the dynamic EL behaviors of carrier injection, carrier transport, carrier relaxation into active region, and carrier recombination at the excited states in active region of LEDs 18,19 . From the results of TREL measurements, nitrogen-polar InGaN/ GaN LEDs with the opposite polarity and nonpolar m-plane InGaN/GaN LEDs with a low polarization effect were shown to provide the advantages of more carrier injection, transport, relaxation, and recombination 18,19 .…”

“…Time-resolved electroluminescence (TREL) measurement under electrical fast pulse excitation is a power tool to explore the dynamic EL behaviors of carrier injection, carrier transport, carrier relaxation into active region, and carrier recombination at the excited states in active region of LEDs 18,19 . From the results of TREL measurements, nitrogen-polar InGaN/ GaN LEDs with the opposite polarity and nonpolar m-plane InGaN/GaN LEDs with a low polarization effect were shown to provide the advantages of more carrier injection, transport, relaxation, and recombination 18,19 . However, the effects of graphene transparent conductive electrodes on the carrier dynamic behaviors of carrier injection, carrier transport, carrier capture into active region, and carrier recombination of InGaN/GaN LEDs with graphene transparent conductive electrodes are not well understood, and many important issues are yet to be studied.…”