deltadoped

Delta-doped, often written as delta-doped or delta-doping, refers to a dopant profile in a solid where donors or acceptors are confined to a very narrow region, effectively forming a two-dimensional sheet of dopants. In semiconductors this corresponds to a near-monolayer thickness along the growth direction, producing a delta-function-like concentration profile and a high local carrier density.

Fabrication is achieved by precise epitaxial growth techniques such as molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). The dopant layer is intentionally placed within a host material, while surrounding regions remain lightly doped or undoped. The dopant distribution is described by a sheet density (donors per square centimeter) rather than a volumetric concentration.

Delta-doped layers are widely used in modulation-doped heterostructures, particularly in III-V systems like GaAs/AlGaAs, where the dopants supply carriers to adjacent undoped regions. This separation reduces impurity scattering in the conduction channel and can create a two-dimensional electron gas with high mobility, enhancing device performance in transistors and other components. The approach is also explored in silicon and other semiconductors to form planar electron gases or sharp interfaces.

Advantages of delta-doping include enhanced carrier confinement, the ability to engineer sharp quantum wells, and improved electrical properties for high-speed devices. Challenges involve maintaining an abrupt, defect-free monolayer during growth and preventing dopant diffusion at higher temperatures, which can broaden the intended profile and degrade performance.

Applications span high-electron-mobility transistors (HEMTs), quantum well devices, infrared detectors, and various nanoscale electronic and optoelectronic systems. Delta-doping remains a key technique for atomic-precision tailoring of electronic properties in semiconductors.