Manipulation of nanoscale V-pits to optimize internal quantum efficiency of InGaN multiple quantum wells

Abstract

We systematically investigated the influence of nanoscale V-pits on the internal quantum efficiency (IQE) of InGaN multiple quantum wells (MQWs) by adjusting the underlying superlattices (SLS). The analysis indicated that high barrier energy of sidewall MQWs on V-pits and long diffusion distance between the threading dislocation (TD) center and V-pit boundary were crucial to effectively passivate the non-radiative centers of TDs. For a larger V-pit, the thicker sidewall MQW on V-pit would decrease the barrier energy. On the contrary, a shorter distance between the TD center and V-pit boundary would be observed in a smaller V-pit, which could increase the carrier capturing capability of TDs. An optimized V-pit size of approximately 200–250 nm in our experiment could be concluded for MQWs with 15 pairs SLS, which exhibited an IQE value of 70%.

3D numerical modeling of the carrier transport and radiative efficiency for InGaN/GaN light emitting diodes with V-shaped pits

“…6(b), which has a good agreement with the experiments. 14,21 With regard to the irregular distribution of TDs in the real epi-layers, the TD density we used is an averaging number. To discuss the influence of TD densities for the overall LED performance, we further simulated 1.0×10 8 cm −2 and 6.25×10 8 cm −2 TD densities, which are corresponding to 1 µm × 1 µm and 700 nm × 700 nm simulation area, respectively.…”

“…20 The influence of V-pit diameters on the efficiency is also discussed by PL measurements. 21 In addition, the atom probe tomography (APT) data indicates that the structure of QWs in V-pit regions is deformed, where the geometry is adjusted, and the width and indium composition of inclined sidewall QWs in V-pits are especially thinner and lower. 22 Moreover, experiments demonstrated that the energy barriers between lateral and sidewall QWs are depending on the V-pit diameter and tried to explain the PL radiative efficiency.…”

“…14 However, it is still vague about how the current path is in the V-pit structure and the trend of PL efficiency with diverse V-pit diameters. 21 Therefore, in this paper we will construct the fully three-dimensional (3-D) model by assessing the real strain distribution, trap-induced potential pulling, and carrier transport equations to discuss the current path because of the non-planar geometry and current spreading effect. 23 The quantum efficiency and turn-on voltage behavior will be studied to explain the experimental data as well as the physics behind.…”

Three dimensional characterization of GaN-based light emitting diode grown on patterned sapphire substrate by confocal Raman and photoluminescence spectromicroscopy

“…On top of the n-GaN layer are 60 pairs of superlattice layers (SLs), which assist the V-pits formation along the TDs. The final layer consists of an InGaN/GaN multi-quantum wells (MQWs) active layer23. There are two groups of quantum wells, each with a different indium composition.…”

Double superstructures in InGaN/GaN nano-pyramid arrays

“…The growth rate of the (1 1 0 1) face was much slower than on the c-plane, the growth rate ratio between the smipolar and c-plane was around 0.1-0.2. The growth rate of semipolar InGaN MQWs on the GaN nanopyramid is significantly influenced by the scale factor of growth condition [22,23]. According to EDS results, the Gallium and Indium element mapping images of the GaN nanopyramid also exhibit high Indium content on c-plane InGaN/GaN NHDs as shown in Fig.…”