Role of oxygen vacancy defect states in the n-type conduction of β-Ga2O3

Abstract

Based on semiempirical quantum-chemical calculations, the electronic band structure of ␤-Ga 2 O 3 is presented and the formation and properties of oxygen vacancies are analyzed. The equilibrium geometries and formation energies of neutral and doubly ionized vacancies were calculated. Using the calculated donor level positions of the vacancies, the high temperature n-type conduction is explained. The vacancy concentration is obtained by fitting to the experimental resistivity and electron mobility.

Polarization of optical spectra in transparent conductive oxide β‐Ga2O3

“…According to the band calculation of β-Ga 2 O 3 [11], the top of the valence band consists entirely of weakly interacting 2p orbitals of oxygen, while the bottom of conduction band has a contribution from 4s orbitals of Ga ions in the octahedra, which create one demensional chain along the b axis. Another calculation of the band structure indicates that over 50 % of electrons at the bottom of conduction band are distributed around the interstitial sites (white space) in Fig.…”

“…Taking account of these results, holes are assumed to be selftrapped in the form of GaO 4 in β-Ga 2 O 3 through strong electron-phonon interaction, while the wavefunctions of conduction electrons are also assumed to be extended from GaO 6 octahedra toward the interstitial sites [11,12].…”

Fabrication and characterization of transparent conductive Sn‐doped β‐Ga2O3 single crystal

“…As for the electrical properties of the β-Ga 2 O 3 single crystals, a number of papers have been reported so far [2,3,[8][9][10]. β-Ga 2 O 3 essentially exhibits an insulating nature for its wide band gap, however oxygen vacancy makes it n-type semiconductor [11], and the conductivity can be controlled from insulating to 38 Ω by changing the oxygen partial pressure of growth atmosphere [3]. In this case, the conduction mechanism is considered to be due to electrons produced by oxygen vacancy.…”

The oxygen vacancy in Ga2O3: a double resonance investigation

“…This explanation is based on the results presented in Ref. 4, where the consequences of the missing oxygen ion on the spatial positions of the surrounding gallium nuclei are calculated on the basis of a variation principle with minimized potential energy. As a result, all nearest neighbors of the vacancy are dislocated up to 16% of the undisturbed atomic distances.…”

“…The Ga ions reside evenly distributed in two different crystallographic sites with tetrahedral (Ga-IV) and octahedral (Ga-VI) coordination with respect to the adjacent O ions, which are arranged in a distorted, cubic-closed, packed lattice and occupy three nonequivalent sites referred to as O(I), O(II) and O(III). 1,2 Pureˇ-Ga 2 O 3 is an insulator with a band gap of ³4.9 eV, 3,4 but when prepared under reducing conditions, oxygen vacancies are created and the compound is converted into an intrinsic n-type semiconductor. The vacancies are compensated by electrons forming shallow donor states in the band gap with an ionization energy of about 30-40 meV and a typical concentration of 10 18 to 10 19 cm 3 at room temperature.…”