Tunnel Junction Width Reduction via Polarization Dipole in GaN

An intermediate layer with different composition (e.g., AlGaN or InGaN) is inserted between the p-type and n-type GaN layers. This intermediate layer acts as a mediator that modifies the band structure and creates a polarization dipole, enabling effective tunneling despite the wide band gap of GaN. The intermediate layer bridges the gap between the heavily doped regions, allowing carrier tunneling while maintaining material compatibility.

The composition of the intermediate layer is optimized to achieve the desired polarization effect. By adjusting the aluminum or indium content in the AlGaN or InGaN layer, the polarization dipole strength is tuned to reduce the effective tunnel width. Additionally, the doping concentrations in the p-type and n-type GaN layers are optimized to achieve degenerate doping levels that maximize tunneling probability.

The intermediate layer with different composition serves as a mediator that enables effective tunneling without requiring extremely high dopant concentrations. The polarization dipole created by the composition gradient in the intermediate layer provides the necessary band alignment, allowing tunneling to occur at dopant levels below the saturation solubility limit.

The doping strategy employs local quality optimization by having different dopant concentrations in different regions. The p-type and n-type GaN layers are degenerately doped to maximize carrier density, while the intermediate layer has a composition gradient that creates the polarization effect. This localized doping approach allows each region to be optimized for its specific function without being constrained by global dopant solubility limits.