Effects of GaN barrier thickness on built-in electric field and internal quantum efficiency of blue InGaN/GaN multiple quantum wells LED structures

Abstract

The built-in electric field in an InGaN quantum well and emission wavelength are numerically evaluated at various GaN barrier thicknesses in blue InGaN/GaN/Al 2 O 3 LED structures. The effect of GaN barrier thickness on the internal quantum efficiency of these structures was studied experimentally by temperature-and excitation-power-dependent photoluminescence measurements. In LED structures with 3-nm-thick GaN barriers in the active region the internal quantum efficiency at high excitation levels higher than that in LED structures with thicker GaN barriers. The results of measurements indicate that in structures with 3-nm-thick GaN barriers, the Auger recombination rate is reduced.

Realization of Highly Efficient InGaN Green LEDs with Sandwich-like Multiple Quantum Well Structure: Role of Enhanced Interwell Carrier Transport

“…Moreover, in the region where the current density is smaller than J max , we can clearly see a noticeable droop in the EQE curve as the thickness of the barriers decreases, especially for sample C, and the droop rate is quite alarming. These results showed an unanticipated phenomenon, that is, as the barrier thickness decreases, the polarization field decreases and the efficiency at low current range should be better …”

“…In addition, compared with samples A and B, sample C has the thinnest barrier thickness corresponding to the A-QWs (13, 10, and 8 nm for samples A, B, and C, respectively). In this case, not only can the carrier tunneling rate R T from CC-QW to A-QW be enhanced, but also the barriers within A-QW’s can be regarded as transparent for carrier transport. , The actual carrier density inside the A-QWs of a sample with a thinner QB should be lower than that of a sample with a thicker QB, even though the effective volume of the active region decreases as the QB thickness decreases. This is because of the enhanced carrier tunneling rate between two types of QWs and the interaction in the A-QWs.…”

“…These results showed an unanticipated phenomenon, that is, as the barrier thickness decreases, the polarization field decreases and the efficiency at low current range should be better. 35 As shown in the left axis of Figure 3(b), we employ a useful parameter called S, i.e., S = Δlog(L)/Δlog (I) (L and I denote the LOP and driven current, respectively). It is said that the value of S at each bias can reflect the dominant carrier recombination process, and when the Shockley Read−Hall (SRH) recombination dominates, the S value is 2.0.…”