Unintentional doping effect in Si-doped MOCVD β-Ga2O3 films: Shallow donor states

Abstract

High-quality β-Ga 2 O 3 films were epitaxially grown by using metalorganic chemical vapor deposition (MOCVD) with different donor concentrations, and their shallow donor states were investigated by the temperaturedependent Hall measurement and secondary ion mass spectroscopy (SIMS) analysis. Two donor levels with ionization energies of ~36 and ~140 meV were extracted. It is found that the unintentional doping (UID) effects in MOCVD contribute substantially to both these two levels: the first donor level may come not only from silicon doping but also from unintentional substitution of carbon for Ga sites, and the second donor level probably comes from doubly charged defects related to unintentional H doping. By analyzing the relationship between the growth conditions and donor states, combined with density functional theory calculations, it is found that reducing the oxygen partial pressure during the growth might be a feasible way to reduce the UID effect. This work paves the way to the precise control of carrier density in Si-doped MOCVD β-Ga 2 O 3 films.

Phase Stabilized MOCVD Growth of β‐Ga2O3 Using SiOx on c‐Plane Sapphire and AlN/Sapphire Template

“…The Si activation annealing did not notably change the conductivity, which is consistent with the report by Gogoba et al, [38] despite Si being a shallow donor in β-Ga 2 O 3 with an activation energy of %36-45 meV. [39,40] The introduction of SiH 4 in the Ga 2 O 3 growth results in no observed change in the material bandgap, maintaining high resistivity, and exhibiting 2θ diffraction peaks related only to β-phase and allowing the growth of a phase pure (201) β-Ga 2 O 3 on sapphire. Such phase stabilization with Si in the form of SiO x has been reported for other binary oxides like HfO 2 .…”

Exploring heteroepitaxial growth and electrical properties of α-Ga2O3 films on differently oriented sapphire substrates

“…The XPS O 1s core level spectra of the films are divided into two individual peaks and well fitted with the sum Gaussian functions. The positions of the two peaks correspond to lattice oxygen of Ga 2 O 3 (O I ) and oxygen vacancies (O II ), respectively [26] . We can use O II /(O I +O II ) to reflect the concentration of oxygen vacancies.…”

“…The main methods currently used to grow Ga 2 O 3 films are radio frequency magnetron sputtering (RFMS) [25,26] , metal organic chemical vapor deposition (MOCVD) [14, 27−29] , molecular beam epitaxy (MBE) [7,8] . Compared to the above methods, pulsed laser deposition (PLD) has the following outstanding advantages: fast film growth, easy doping, easy preparation of films with the same stoichiometric ratio as the target, easy adjustment of the growth process [10,11,13,30] .…”

Potential design strategy of wide-bandgap semiconductor p-type β-Ga2O3

“…β-Ga 2 O 3 typically exhibits n-type conductivity and these donor defects can spontaneously compensate for intrinsic acceptor defects or p-type dopants, thereby limiting the p-type conductivity of β-Ga 2 O 3 . The n-type conductivity defects in β-Ga 2 O 3 originate from inherent deep donor defects (including oxygen vacancies, Vo) as well as unintentional n-type shallow donor impurities (such as Si and H et al) introduced during the fabrication process [6,46,47]. In the detailed discussion of the crystal structure of β-Ga 2 O 3 in the section 2.1, oxygen vacancies with two threefold coordinated (OI and OIII) and one fourfold coordinated (OII) were initially considered as shallow donors and the reason for n-type conductivity in present researches.…”