Mg-doping and free-hole properties of hot-wall MOCVD GaN

TL;DR

This study explores Mg doping in GaN grown by hot-wall MOCVD, revealing how growth conditions affect impurity incorporation, defect formation, and electrical properties, enabling high-quality p-type GaN for power electronics.

Contribution

It provides a comprehensive analysis of Mg incorporation, defect interactions, and electrical properties in GaN:Mg grown by hot-wall MOCVD, with optimized conditions for p-type conductivity without annealing.

Findings

Achieved high Mg doping levels up to 1.10×10^{20} cm^{-3}

Demonstrated p-type conductivity in as-grown GaN:Mg without annealing

Produced low-resistivity, high free-hole density p-GaN layers after annealing

Abstract

The hot-wall metal-organic chemical vapor deposition (MOCVD), previously shown to enable superior III-nitride material quality and high performance devices, has been explored for Mg doping of GaN. We have investigated the Mg incorporation in a wide doping range ($2.45\times{10}^{18}~cm^{-3}$ up to $1.10\times{10}^{20}~cm^{-3}$) and demonstrate GaN:Mg with low background impurity concentrations under optimized growth conditions. Dopant and impurity levels are discussed in view of Ga supersaturation which provides a unified concept to explain the complexity of growth conditions impact on Mg acceptor incorporation and compensation. The results are analysed in relation to the extended defects, revealed by scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and surface morphology, and in correlation with the electrical properties obtained by Hall effect and capacitance-voltage (C-V) measurements. This allows to establish a comprehensive picture of GaN:Mg growth by hot-wall MOCVD providing guidance for growth parameters optimization depending on the targeted application. We show that substantially lower H concentration as compared to Mg acceptors can be achieved in GaN:Mg without any in-situ or post-growth annealing resulting in p-type conductivity in as-grown material. State-of-the-art $p$-GaN layers with a low-resistivity and a high free-hole density (0.77 $\Omega$.cm and $8.4\times{10}^{17}~cm^{-3}$, respectively) are obtained after post-growth annealing demonstrating the viability of hot-wall MOCVD for growth of power electronic device structures.