Polarity control by inversion domain suppression in N-polar III-nitride heterostructures

TL;DR

This paper investigates polarity control in N-polar III-nitride heterostructures, demonstrating suppression of inversion domains through thermodynamic and growth condition optimization, enabling high-quality heterostructures for high-power applications.

Contribution

It introduces a novel polarity control strategy using thermodynamic Al supersaturation and substrate misorientation to suppress inversion domains in N-polar III-nitride growth.

Findings

Inversion domains are suppressed at high-temperature AlN nucleation layers.

Step-flow growth mode achieved on off-axis substrates leads to polarity control.

High-quality N-polar heterostructures are successfully fabricated.

Abstract

Nitrogen-polar III-nitride heterostructures offer advantages over metal-polar structures in high frequency and high power applications. However, polarity control in III-nitrides is difficult to achieve as a result of unintentional polarity inversion domains (IDs). Herein, we present a comprehensive structural investigation with both atomic detail and thermodynamic analysis of the polarity evolution in low- and high-temperature AlN layers on on-axis and 4$^{\circ}$ off-axis Carbon-face 4H-SiC (000$\bar{1}$) grown by hot-wall metal organic chemical vapor deposition. A polarity control strategy has been developed by variation of thermodynamic Al supersaturation and substrate misorientation angle in order to achieve desired growth mode and polarity. We demonstrate that IDs are totally suppressed for high-temperature AlN nucleation layers when step-flow growth mode is achieved at the off-axis. We employ this approach to demonstrate high quality N-polar epitaxial AlGaN/GaN/AlN heterostructures.