Surface-Induced Carrier Localization and Recombination Characteristics in InGaN/GaN Quantum Dots in Nanopillars

Abstract

In quantum structures and nanomaterials, surface conditions have significant influence on the material’s optical and electrical properties; hence, surface modification is an inevitable and critical step during the fabrication process of optoelectronic devices. A comprehensive understanding on how surface conditions impact on the performance is a key issue; however, it is difficult to apply experimental techniques to study the surface physics in the atomic scale. In this paper, the photoluminescence properties of InGaN/GaN quantum dots in nanopillar samples were carefully investigated and compared after applying various surface manipulation techniques. Spectroscopic results show that the localization features including recombination energy level and peak shift with temperature are extremely sensitive to surface treatment. Based on the localized state ensemble model, a quantitative analysis is performed taking into account of thermal activation and density of states distribution function of localization. The correlation between optical properties and the physical mechanism of surface modification is established. This spectroscopic technique along with the analytical method provides physical insights and reliable basis for nanoscale device evaluation and optimization.

Asymmetric Broadening and Enhanced Photoluminescence Emission in ZnO Due to Electron–Phonon Coupling

“…In addition, the emission mechanism of electron–phonon coupling not only appears in ZnO-related materials but also widely exists in materials with strong phonon interaction. GaN-based materials with high emission efficiency are also severely affected by localization effects, as in the case of the carrier distribution in this paper. It is generally accepted that carrier localization prevents nonradiative recombination; thus, high quantum efficiency is guaranteed. ,− In this paper, the understanding of the correlation between carrier localization and luminescence enhancement is further improved.…”

Time–Energy Quantum Uncertainty: Quantifying the Effectiveness of Surface Defect Passivation Protocols for Low-Dimensional Semiconductors

“…In fact, GaN-based nanowires generally suffer from oxygen and nitrogen vacancies (V O,N ) that act as surface defect states . As a consequence, surface passivation would improve the photoemission characteristics and reduce its peak width. − It is worth noting that when nanowire surfaces are passivated, no additional radiative centers are introduced because the density of states (DOS) in the valence and conduction band edges remain unchanged ( D 1D ( E ); while nanowire surfaces are two-dimensional (2D)). Rather, the intensity of photoemission is affected.…”