Study of the Excitation Power Dependent Internal Quantum Efficiency in InGaN/GaN LEDs Grown on Patterned Sapphire Substrate

Abstract

Abstract-The mechanisms of the excitation power dependent internal quantum efficiency in InGaN/GaN multiple quantum wells (MQWs) LEDs grown on the planar and the patterned sapphire substrates (PSS) at temperature of 15 and 300 K were investigated. From observation the tendency of emission peak energy and carrier lifetime variation in MQWs with different excitation power for both LED samples, we conclude the internal quantum efficiency would increase as coulomb screening effect dominates at lower carrier injection stage and decrease due to the band-filling effect at higher density stage. At room temperature, the majority of the initial injected carriers would be first consumed by the thermal activated nonradiative centers that hinder the further achievement of high-efficiency LED devices. Experimentally, the internal quantum efficiency of the LED grown on the PSS is ∼70% and that of the LED grown on the planar sapphire substrate is ∼62%. For the LED grown on the PSS, the observed higher internal quantum efficiency is due to the larger activation energy Therefore, the reduction of dislocation defects and the prevention of injected carriers escaping from extended states would be a promising prospective for InGaN/GaN MQWs LEDs to achieve high internal quantum efficiency.

Internal quantum efficiency enhancement of GaInN/GaN quantum-well structures using Ag nanoparticles

“…This effect is attributed to coulomb screening of the quantum-confined stark effect (QCSE) by the increasing carrier density. 28 Fig . 5(b) shows the IQE enhancements with changing excitation power density.…”

Study of the internal quantum efficiency of InGaN/GaN UV LEDs on patterned sapphire substrate using the electroluminescence method

“…In PL IQE measurements, since PL efficiency was almost constant for temperatures below 30 K, here we used 15 K as LT, and for EL IQE, we chose 77 K as the LT since the maximum relative IQE occurred at about 77 K. The definition of carrier density in EL measurement is the injected carrier divided by the active volume, while in PL measurement, we adopted the method in Ref. [7].…”

“…Details of the PL IQE measurement and the definition of injected carrier density were published in Ref. [7].…”

Synthesis of cadmium selenide quantum dots for fabrication of hybrid light emitting diodes.

“…None of this would have been possible without her help. Figure 1: TEM image of a CdSe QDs synthesized using the hot injection method [3] ...... 3 …”

“…When compared with other conventional devices such as InGaN/GaN LEDs with an internal quantum efficiency of 70% [3], the use of quantum dots becomes quite lucrative.…”