Impact of Dangling Bonds on the Electronic Structure of III-V Quantum Dots

By Norick De Vlamynck, Jordi Llusar, Ivan Infante, and Zeger Hens

Quantum dots are at the heart of next-generation technologies, from high-resolution displays to infrared sensors. However, many of the most efficient systems rely on toxic heavy metals, limiting their widespread use. III–V quantum dots offer a safer alternative, with tunable optical properties and compatibility with solution-based processing. Yet, their performance has long been hindered by poorly understood surface defects. In this work, we uncover how anion dangling bonds – unsatisfied atomic bonds at the surface – fundamentally shape the electronic structure of III–V quantum dots.

While global research has primarily focused on InP and InAs QDs, colloidal synthesis protocols now extend to InSb and Ga-based III-V compounds. Interestingly, different materials can produce the same emission color: for example, both InP and GaAs quantum dots can emit red light. This flexibility opens the door to optimizing device performance without changing operational wavelengths.

Figure 1: Electronic structure of InP-1116. (a) InP-1116 model quantum dot, highlighting the (100), (111) and P(-1-1-1) facets. (b) Reciprocal space path followed to determine the Bloch orbital expansion coefficients. (c) Fuzzy band structure of InP-1116 calculated through Bloch orbital expansion. The higher energy (conduction) bands overlap with the dashed bulk InP bands, while a range of orbitals appears above the lower energy (valence) band edge. (d) Partial density of states (pDOS), revealing the increased contribution of the P(-1-1-1) facets for the mid-gap orbitals.

As-synthesized InP QDs typically exhibit negligible photoluminescent properties. Using large-scale density functional theory (DFT) simulations on the Vlaams Supercomputer Centrum, we analyzed the electronic structure of InP quantum dots and found that unpassivated P(-1-1-1) facets are responsible for the formation of mid-gap orbitals (Figure 1). These orbitals are highly localized at the surface and disrupt the ideal electronic structure of the material. By visualizing the electronic structure through the Bloch orbital expansion, we could clearly distinguish between surface-localized orbitals and those resembling the bulk semiconductor. This allowed us to define a surface-band orbital width Δ_SBO, a quantitative measure of how strongly surface defects affect the electronic structure.

Figure 2: Screening of III-V quantum dots. (a) Color map representing the pDOS of the atoms in the (-1-1-1) facets as a function of the orbital index, obtained from the electronic structure of the 9 different III-V QD-1116 models. (b) Surface-band orbital width Δ_SBO, defined as the energy difference between the HOMO and the first-delocalized occupied orbital, for the QD-1116 models. (c) Color map of Δ_SBO as a function of the QD model size for Ga-based and In-based III-V compositions.

Extending our analysis to nine different III-V semiconductors, ranging from AlP to InSb, revealed that the susceptibility to these surface orbitals strongly depends on composition. Where the (-1-1-1) facets are detrimental to the Al-based compounds, an increasing facet tolerance is observed for P < As < Sb and Al < In < Ga-based materials (Figure 2). When we also account for quantum dot size, where larger dots expose more surface area and thus more dangling bonds, GaSb, InSb, and GaAs emerge as the most promising candidates, combining favorable electronic properties with increased tolerance to surface defects.

Role of VSC

Access to extensive VSC Tier-1 resources allowed us to screen the electronic structure of an entire family of III-V quantum dots, pointing Ga-based III-V quantum dots as the next-generation materials for short-wave infrared sensors, imagers and light sources.

Publication: De Vlamynck, N., Llusar, J., Infante, I., & Hens, Z. (2026). Impact of Dangling Bonds on the Electronic Structure of III-V Quantum Dots. MATSUS Spring 2026 Conference Presentation.

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