APS Journals

The earliest APS contributions to the defect physics of insulators and semiconductors addressed color centers in alkali halide crystals, providing a coherent theoretical framework for phenomena that had previously been considered across several distinct experimental and chemical traditions.

Early studies of carrier recombination in semiconductors revealed that structural imperfections decreased the charge-carrier lifetime. Physical Review papers from Hall and from Shockley and Read quantified how point defects influence the recombination of injected charge carriers, an insight that proved foundational to the development of semiconductor devices.

The post-war decades were characterized by atomic-scale identification of semiconductor defects through experimental techniques including electron paramagnetic resonance, electron-nuclear double resonance, and photocapacitance. These measurements established the microscopic structures, charge states, and symmetry distortions of specific defects, providing an experimental foundation against which later theoretical developments would be tested.

Beginning in the late 1970s, Green’s-function and scattering-theoretic approaches demonstrated that the electronic structure of an isolated defect in a real crystal could be treated self-consistently. This period established the theoretical infrastructure on which subsequent density-functional-theory-based defect calculations would be built and produced a major comprehensive review in the field.

The adoption of density functional theory within a periodic supercell framework during the late 1980s and 1990s transformed defect calculations into a widely used approach across solid-state physics and materials chemistry. The chemical-potential-dependent formation-energy formalism introduced during this period underpins much of the modern computational treatment of point defects. Subsequent decades saw studies published in APS journals challenge established interpretations of defect behavior in a range of semiconductors, identify the limitations of standard exchange-correlation functionals for defect calculations, and develop the correction schemes required for quantitative treatment of charged defects.

A 2014 Reviews of Modern Physics article consolidated much of the methodological development of the preceding two decades and remains a widely used reference for first-principles defect calculations, providing the fourth major review in the field following those of Seitz, Pantelides, and Fahey.

Developments over the past decade have extended defect calculations beyond static formation energies and electronic transition levels toward direct prediction of functional properties. The first-principles treatment of nonradiative carrier capture developed during this period provided a route toward calculating Shockley-Read-Hall recombination rates from electronic-structure theory, complementing the earlier phenomenological treatment of carrier capture developed during the spectroscopic era.

Building on the landmark results described above, the study of point defects remains an important topic across a range of functional materials and applications. This research particularly impacts the control of semiconductor performance for tailored applications in quantum information, renewable energy systems, and electronic devices. Here, our editors highlight a selection of recent point defect research published across the portfolio between 2023 and 2026. The sections below are organized by application area rather than chronology, with brief introductions to each for readers coming to point defects from adjacent fields.

Wide-band-gap semiconductors can host point defects with optically addressable spin states. These spin defects interact with the environment to sense other spins and magnetic fields, enabling quantum sensing and quantum spin control. Visible and ultraviolet light can probe and manipulate these spin defects; this optical response has been used to create solid-state optical qubits for quantum computing. Ongoing research explores the creation and control of these spin defects, their interactions, and their viability for emerging quantum technologies.

Diamond is an ultrastable host for vacancy-related spin defects, including the widely studied nitrogen-vacancy (NV⁻) center and group-IV split-vacancy centers. Spin defects in diamond can exhibit long coherence times, on the order of milliseconds at room temperature. Active research seeks to precisely control their generation and interactions and looks toward their integration into advanced technologies.

Beyond diamond, other wide-band-gap semiconductors in the carbide and nitride families can host spin defects. These materials offer advantages in designed semiconductor fabrication for defect control and photonic manipulation but may suffer from shorter coherence times. New research on carbide- and nitride-based defects explores a wider family of materials and introduces two-dimensional materials as spin-defect hosts.

Emerging research explores spin and optical defects in a wide range of material families. These studies highlight new theoretical frameworks and experimental approaches that enable the creation and understanding of the next generation of quantum defects.

The optical emission of the NV⁻ center in diamond varies with the local magnetic or electric field, and the defect’s sensitivity, long lifetime, and optical addressability have made it a practical quantum sensor. These capabilities have been applied to provide a frequency reference, to map the properties of superconducting materials, and to sense magnetic fields in a living animal for medical imaging.

Charge generation and transport are central to the performance of semiconductor materials for renewable energy applications. Across energy generation, transformation, and storage technologies, point defects influence the flow of charge carriers. These highlighted studies use a combination of experimental and computational approaches to understand why some defects harm the performance of energy materials, why others have no apparent effect, and why still others enable the desired performance.

As device requirements move beyond the performance limits of silicon, alternative electronic materials have become increasingly important. III-V semiconductors like (In,Ga)As offer a tunable band gap and high mobility, while wide-band-gap semiconductors like Ga₂O₃ are suited for high-performance power electronics. Control of point defects in these materials underpins the design of these devices.

The growing interdisciplinary interest noted above brings researchers to point defects from adjacent fields, where the conventions of defect and defect level diagrams are not always familiar. A shared language and pedagogical framing such as those presented in this Tutorial will support that expansion.