Effects of a Si-doped InGaN Underlayer on the Optical Properties of InGaN/GaN Quantum Well Structures with Different Numbers of Quantum Wells

Abstract

In this paper we report on the optical properties of a series of InGaN polar quantum well structures where the number of wells was 1, 3, 5, 7, 10 and 15 and which were grown with the inclusion of an InGaN Si-doped underlayer. When the number of quantum wells is low then the room temperature internal quantum efficiency can be dominated by thermionic emission from the wells. This can occur because the radiative recombination rate in InGaN polar quantum wells can be low due to the built-in electric field across the quantum well which allows the thermionic emission process to compete effectively at room temperature limiting the internal quantum efficiency. In the structures that we discuss here, the radiative recombination rate is increased due to the effects of the Si-doped underlayer which reduces the electric field across the quantum wells. This results in the effect of thermionic emission being largely eliminated to such an extent that the internal quantum efficiency at room temperature is independent of the number of quantum wells.

Polar ( In , Ga ) N / Tanner1, Dawson2, Kappers3 et al. 2020Phys. Rev. AppliedSelf Cite

“…One such countermeasure is for instance the already widely used approach of underlayers. 32,77,78 It has been shown that via the use of underlayers the point defect density can be reduced in the QWs, which should then be beneficial for the green gap problem. Furthermore, on the finding of a relatively large electron localization lengths and the potential connection to nonradiative recombination rate, tailoring carrier localization effects might be the way forward to close the green gap.…”

Role of surface defects in the efficiency degradation of GaInN-based green LEDs

“…Previously, a remarkable increase of IQE in GaInN-based visible LEDs was demonstrated by introducing GaInN underlying layers (ULs) underneath the GaInN/GaN multiple quantum well (MQW) active region. [10][11][12][13] For instance, by introducing GaInN ULs, ∼85% and ∼35% enhancements in electroluminescence (EL) efficiency were reported for green and blue LEDs, respectively. 14,15) Some of the mechanisms used to explain the effect of UL introduction on EL efficiency include strain relaxation, 16) efficient electron injection, 17) and dislocation termination.…”