Luminescence properties of thick InGaN quantum‐wells

Abstract

In this paper, we discuss the physics of recombination in thick InGaN quantum-well (QW) based structures. Thick InGaN QWs have been suggested as one concept to reduce the typical decrease of internal efficiency of InGaN based light emitters towards high current densities. We show that at typical operation current densities, recombination in such thick QWs mainly originates from excited QW-states, which exhibit good electron hole overlap and large spatial extent, enabling a reduction of carrier density. We identify these states by comparing current dependent electroluminescence spectra to band structure simulations. The reduction of carrier density is verified by measuring current dependent carrier lifetimes. We find that saturation of efficiency is reduced for increasedQWthickness. However, the same effect can also be achieved using an MQW structure optimized for real MQW emission. We conclude that regardless of the employed concept, a decrease in carrier density is central to improve the high current efficiency of InGaN based light emitters

Green high‐power light sources using InGaN multi‐quantum‐well structures for full conversion

“…This interpretation is confirmed by Fig. 3, which shows carrier lifetimes, obtained under electrical small-signal modulation [9], as a function of the www.pss-c.com current density per QW. Such a normalized excitation density axis ensures comparable carrier generation rates per QW for the electrically and optically pumped structures.…”

On the origin of IQE‐‘droop’ in InGaN LEDs

“…In consequence, to further proove the hypothesis of a quantum well internal Auger-like loss process, we produced a 10 nm thick SQW and an 8-fold MQW sample. We compared their high current emission power saturation to that of a 2 nm SQW sample [15]. We used samples emitting at wavelengths around 400 nm to guarantee comparable material quality.…”

Investigation of the carrier distribution in InGaN‐based multi‐quantum‐well structures

“…Many experimental findings point to an Auger effect being the root cause of the droop, although there is still no clear consensus [1,2]. In any case, considerable progress has been achieved by the use of MQW structures, which allow a reduction of the carrier density in the active region at operation current density [3]. However, a homogeneous carrier distribution over a larger number of QWs is hard to achieve [4][5][6].…”