Structural and optoelectronic characteristics of β-Ga2O3 epitaxial films with Zn alloying and subsequent oxygen annealing

Abstract

Pure and ∼7.5 at% Zn alloyed β-Ga₂O₃ epitaxial films were epitaxially grown by metal organic chemical vapor deposition choosing sapphire (c-plane) as substrates, followed by 600 °C annealing in an oxygen atmosphere. We have characterized the structural, optical and electrical properties of the four prepared samples including as-grown pure β-Ga₂O₃, annealed pure β-Ga₂O₃, as-grown β-Ga₂O₃:Zn and annealed β-Ga₂O₃:Zn films in detail. Furthermore, solar-blind UV photodetectors with metal–semiconductor–metal structures fabricated from these epitaxial thin films have been demonstrated. A giant performance enhancement can be observed for β-Ga₂O₃ photodetectors by Zn alloying and subsequent oxygen annealing. The device fabricated from the annealed β-Ga₂O₃:Zn film shows a low dark current of ∼3.7 × 10⁻¹¹ A, a high responsivity of 2.8 × 10³ A W⁻¹ and a high UV-vis rejection ratio of 5.6 × 10⁵ at 10 V bias. And an ultra-high specific detectivity up to 5.9 × 10¹⁶ cm Hz^1/2 W⁻¹ (Jones) is observed. Such excellent photodetection performance of annealed Ga₂O₃:Zn devices can be explained by the donor compensation effect and the deep level trap removal effect by the introduction of Zn. Our findings contribute a roadmap for realizing high-performance Ga₂O₃-based solar-blind photodetectors, and provide a sturdy foundation for future applications.