Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

Abstract

Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga-and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED. V

Effects of Thickness of a Low-Temperature Buffer and Impurity Incorporation on the Characteristics of Nitrogen-polar GaN

“…III-Nitride semiconductors have been used for light-emitting diodes (LEDs), laser diodes, solar cells, and high electron mobility transistors (HEMTs) [1–4]. These nitride devices are generally grown along the polar c -axis ( Ga -polar), where the built-in polarization field decreases the overlap of the electron and hole wave functions and leads to quantum-confined Stark effect (QCSE) [1–4].…”

“…These nitride devices are generally grown along the polar c -axis ( Ga -polar), where the built-in polarization field decreases the overlap of the electron and hole wave functions and leads to quantum-confined Stark effect (QCSE) [1–4]. Meanwhile, the reverse polarization field of Nitrogen ( N )-polar III-nitrides along the - c -axis [000-1] can be used for device applications, such as enhancement mode and highly scaled transistors, photodetectors, Zener tunnel diodes, and sensors [5–7].…”

“…Meanwhile, the reverse polarization field of Nitrogen ( N )-polar III-nitrides along the - c -axis [000-1] can be used for device applications, such as enhancement mode and highly scaled transistors, photodetectors, Zener tunnel diodes, and sensors [5–7]. Due to the reversed direction of the polarization field, a larger forward bias reduces QCSE in N -polar quantum wells (QWs), increasing overlap of electron and hole wave function [4]. By time-resolved electroluminescence measurement, an N -polar LED has been shown to have more efficient carrier relaxation and faster carrier recombination [4].…”

“…Due to the reversed direction of the polarization field, a larger forward bias reduces QCSE in N -polar quantum wells (QWs), increasing overlap of electron and hole wave function [4]. By time-resolved electroluminescence measurement, an N -polar LED has been shown to have more efficient carrier relaxation and faster carrier recombination [4]. …”

“…Because of the low-quality epitaxial layers of N -polar GaN, the device performance of the N -polar LED is poor compared to that of the Ga -polar LED [4]. The incorporation of oxygen in N -polar GaN during nitridation is much larger than that in Ga -polar GaN [10, 11].…”