Spectral and Small-Signal Electroluminescence Analysis of Carrier Dynamics in Dual-Color InGaN/GaN Light-Emitting Diodes

TL;DR

This study investigates carrier dynamics in dual-color InGaN/GaN LEDs using spectral and small-signal electroluminescence analysis, revealing how emission characteristics vary with current density and how carrier distribution is non-uniform across quantum wells.

Contribution

It provides new insights into carrier transport, distribution, and recombination mechanisms in dual-color InGaN/GaN LEDs, highlighting the limited interwell transport and active region composition.

Findings

Green emission dominates at low current densities.

Blue emission becomes more prominent at higher current densities.

Active region consists of 2-3 quantum wells with limited interwell transport.

Abstract

We study carrier transport, distribution, and recombination in dual-color c-plane InGaN/GaN LEDs using spectral analysis and small-signal electroluminescence (SSEL). The emissions from green and blue quantum wells (QWs) were experimentally separated and analyzed. Spectral analysis and SSEL independently demonstrate that emission from the green QW is dominant at low current densities due to its narrower bandgap, while emission from the blue QW is more significant at higher current densities due to its reduced quantum confined stark effect (QCSE) and larger wavefunction overlap. In addition, we demonstrate that the carrier recombination in the QWs is non-uniform, with carrier transport dramatically affecting the carrier distribution between QWs and the recombination in a specific QW. Finally, we also show that the effective active region in these V-pit-engineered InGaN/GaN LEDs is roughly 2 to 3 QWs on the p-GaN side, with limited interwell carrier transport and recombination in additional QWs.