Polarization-balanced design of AlN/GaN heterostructures: Application to double-barrier structures

TL;DR

This paper introduces polarization-balanced design principles for AlN/GaN heterostructures to optimize electronic transport by avoiding depletion regions, demonstrated through double-barrier structures with theoretical guidance on alloy composition.

Contribution

It presents a systematic approach to design polar heterostructures that prevent depletion regions by matching bias with polarization-induced voltage drops, specifically applied to AlN/GaN double barriers.

Findings

Polarization-balanced designs prevent depletion regions.

Derived relation guides alloy composition for desired voltage drop.

Designs improve ground state filling and active region emptying.

Abstract

Inversion- and depletion-regions generally form at the interfaces between doped leads (cladding layers) and the active region of polar heterostructures like AlN/GaN and other nitride compounds. The band bending in the depletion region sets up a barrier which may seriously impede perpendicular electronic transport. This may ruin the performance of devices such as quantum-cascade lasers and resonant-tunneling diodes. Here we introduce the concepts of polarization balance and polarization-balanced designs: A structure is polarization balanced when the applied bias match the voltage drop arising from spontaneous and piezeolectric fields. Devices designed to operate at this bias have polarization-balanced designs. These concepts offer a systematic approach to avoid the formation of depletion regions. As a test case, we consider the design of AlN/GaN double barrier structures with Al$_{\tilde{x}}$Ga$_{1-\tilde{x}}$N leads. To guide our efforts, we derive a simple relation between the intrinsic voltage drop arising from polar effects, average alloy composition of the active region, and the alloy concentration of the leads. Polarization-balanced designs secure good filling of the ground state for unbiased structures, while for biased structures with efficient emptying of the active structure it removes the depletion barriers.