Deltadoping

Deltadoping, or delta doping, is a semiconductor fabrication technique in which dopant atoms are confined to an ultrathin, ideally atomically thin, layer within a host material. The dopant sheet is introduced during epitaxial growth by methods such as molecular beam epitaxy (MBE) or chemical vapor deposition (CVD), producing a high dopant concentration in a single plane while keeping the surrounding material relatively undoped.

Because dopants are confined to a narrow plane, the conduction-band silhouette bends to form a two-dimensional carrier gas—electrons or holes—in nearby regions. In many systems, delta-doping is used together with modulation doping to separate ionized dopants from the conducting channel, thereby enhancing carrier mobility and reducing impurity scattering.

Common materials and realizations include GaAs/AlGaAs and other III-V heterostructures, where silicon or similar dopants are delta-doped in the AlGaAs layer to supply electrons that populate a high-mobility two-dimensional electron gas at the GaAs interface. Delta-doping is also implemented in silicon-based and other semiconductor platforms to engineer sharp carrier profiles for specialized devices.

Advantages of delta-doping include the ability to achieve high sheet carrier densities with a sharply confined dopant region, improved mobility in the conducting channel due to spatial separation from dopants, and precise control over carrier distribution for quantum-well and nanoelectronic architectures. These features have enabled the development of high-speed devices such as modulation-doped transistors and devices relying on two-dimensional electron gases.

Challenges involve diffusion and intermixing of dopants during subsequent processing, control of ultrathin layer thickness, interface roughness, and maintaining precise dopant placement under realistic thermal budgets. The technique remains central to heterostructure engineering and quantum-scale device design.