Polarization doping ab initio verification of the concept charge conservation and nonlocality

TL;DR

This paper theoretically investigates polarization doping in graded AlxGa1-xN layers, confirming charge conservation and nonlocal effects, and demonstrating its potential for high-conductivity optoelectronic devices without impurity doping.

Contribution

It provides an ab initio verification of polarization doping, highlighting its nonlocal charge compensation and practical advantages for device engineering.

Findings

Charge conservation applies to fixed and mobile charges separately.

Polarization doping can achieve high carrier densities without impurity doping.

Potential for high mobility and conductivity in optoelectronic devices.

Abstract

In this work, we study the emergence of polarization doping in AlxGa1-xN layers with graded composition from a theoretical viewpoint. We demonstrate that the charge conservation law applies for fixed and mobile charges separately, leading to nonlocal compensation phenomena involving bulk fixed and mobile charge and polarization sheet charge at the heterointerfaces. The magnitude of the effect allows obtaining technically viable mobile charge density for optoelectronic devices without impurity doping (donors or acceptors). Therefore, it provides an additional tool for the device designer, with the potential to attain high conductivities: high carrier concentrations can be obtained even in materials with high dopant ionization energies, and the mobility is not limited by scattering at ionized impurities.