The Growth of Ga2O3 Nanowires on Silicon for Ultraviolet Photodetector

Abstract

We investigated the effect of silver catalysts to enhance the growth of Ga2O3 nanowires. The growth of Ga2O3 nanowires on a P+-Si (100) substrate was demonstrated by using a thermal oxidation technique at high temperatures (~1000 °C) in the presence of a thin silver film that serves as a catalyst layer. We present the results of morphological, compositional, and electrical characterization of the Ga2O3 nanowires, including the measurements on photoconductance and transient time. Our results show that highly oriented, dense and long Ga2O3 nanowires can be grown directly on the surface of silicon. The Ga2O3 nanowires, with their inherent n-type characteristics formed a pn heterojunction when grown on silicon. The heterojunction showed rectifying characteristics and excellent UV photoresponse.

Comparative Study of Growth Morphologies of Ga2O3 Nanowires on Different Substrates

“…The growth morphologies of gallium oxide were studied on various substrates and at different oxidation temperatures. Previous work has shown that crystalline the Ga 2 O 3 phase was obtained under the same oxidation conditions used in this work [ 2 , 22 ]. Because the oxidation conditions were kept constant in this work, the nanostructures formed during oxidation are primarily related to the substrate.…”

“…We should mention that the SEM image of the Ga 2 O 3 NWs on SiO 2 /Si was taken at the border between the Ag-coated surface and the SiO 2 surface, which emphasizes the catalyst effect of Ag on the growth of Ga 2 O 3 NWs [ 18 ]. Although, it has been shown that sputtered Ag thin film plays a major role in enhancing wettability of the surface and leads to a homogeneous coating of Ga 2 O 3 nanowires [ 22 ]. Using liquid Ag on the top or bottom of liquid Ga showed a nonuniform coating of silicon or quartz as shown for N-Si and SiO 2 -Si ( Figure 2 and Figure 3 ).…”

“…The growth of Ga 2 O 3 on substrates was greatly affected by the presence of an Ag thin film, which was introduced in this system to modify the local energy properties at the substrate/nucleus interface. Alhalaili et al [ 22 ] discussed the growth mechanism of Ga 2 O 3 nanowires in more detail. The physical interactions between Ga, Ag, and O, and the stability of various phases formed during the oxidation of Ga in the presence of Ag brings new challenges in the formulation of a unitary oxidation mechanism for the growth Ga 2 O 3 nanostructures.…”

“…During the oxidation of the substrates in the presence of Ag, additional temperature-dependent processes influenced both the nucleation and the growth of nanostructures. Ga 2 O 3 nucleation in the presence of Ag was greatly influenced by the oxidation temperatures due to the high oxygen diffusivity and solubility in silver at higher temperatures [ 2 , 22 ].…”

“…Although no Ag nanoparticles were visibly detected on the surface of the nanowire, Ag can be incorporated in Ga 2 O 3 nanowires. Because the Ag-Si phase diagram shows a eutectic reaction at 845 °C, silicon can therefore react with silver at the oxidation temperature of 950 °C to form a solid solution [ 22 , 34 ]. Consequently, the presence of silicon in Ga 2 O 3 nanowires may be increased unintentionally, as an impurity that corresponds strongly to n-type conductivity [ 35 ].…”