Tunable electronic, transport, and optical properties of fluorine- and hydrogen-passivated two-dimensional Ga₂O₃ by uniaxial strain

Abstract

Two-dimensional (2D) semiconductors have shown great prospect in future-oriented optoelectronic applications, whereas the applications of conventional 2D materials are significantly impeded by the low electron mobility (≤ 200 cm2V1s1). In this work, strain mediated fluorine and hydrogen passivated 2D Ga2O3 systems (FGa2O3H) have been explored via using first-principles calculations with the Heyd-Scuseria-Ernzerh (HSE) and Perdew-Burke-Ernzerhof (PBE) functional. Our results reveal a considerable high electron mobility of FGa2O3H up to 4863.05 cm2V1s1 as the uniaxial tensile strain reaches 6%, which can be attributed to the enhanced overlapping of wave functions and bonding features. Overall, applying the uniaxial strain monotonously along a(b) direction from compressive to tensile cases, the bandgaps of 2D FGa2O3H increase initially and then decrease, which is originated from the changes of σ* anti-bonding in the CBM and π bonding states in the VBM accompanying with the lengthening Ga-O bonds. Additionally, when the tensile strain is larger than 8%, the stronger π bonding at G point leads to an indirect-to-direct transition. Besides the highest electron mobility of n-type doped 2D FGa2O3H with 6% tensile strain, the electrical conductivity is enhanced and further elevated with the temperature increase from 300K to 800K. The variations of the absorption coefficient in the ultraviolet region is negligible with the increasing tensile strain from 0% to 6%, shed light on its applications in high-power optoelectronic devices.

Ultra-high electron mobility in Sn-doped two-dimensional Ga2O3 modified by biaxial strain and electric field

“…When 8% tensile strain is applied, μ ey exhibits a maximum value of 22579.32 cm 2 V −1 s −1 , which is much higher than the values that have been explored in Ga 2 O 3 with other dopants, such as the F dopant of ~300 cm 2 V −1 s −1 , 52) the Cl dopant of 5177.71 cm 2 V −1 s −1 , 52) as well as the H and F co-dopant of 4863.05 cm 2 V −1 s −1 in our recent work. 36) When 8% compressive strain is applied, μ ex has the lowest value of 888.38 cm 2 V −1 s −1 , which is still larger than those of conventional 2D materials, e.g., MoS 2 (∼200 cm 2 V −1 s −1 ), 53) WS 2 (246 cm 2 V −1 s −1 ), 54) and GaN (∼300 cm 2 V −1 s −1 ). 55) Our results thus suggest that strain is an effective mediation to modulate the carrier mobility in 2D Ga 2 O 3 material, whilst 2D Ga 2 O 3 exhibits significant prospects in nanoscale electronic applications.…”

“…32) For comparison, electronic structures of undoped Ga 2 O 3 and Sn-doped Ga 2 O 3 are adjusted utilizing the screened Heyd-Scuseria-Ernzerh (HSE) hybrid density functional and GGA+U method to correct the bandgap. As suggested in the literature, the mixing parameter for HSE calculation is set at 35%, 28,36) while 7 eV and 8.5 eV for Ga-3d and O-2p orbitals, as well as a typical 7 eV value for Sn-4d orbital, are applied for the GGA+U calculation. [37][38][39] The formation energies E f of Sn-doped 2D Ga 2 O 3 configurations are calculated as 39,40)…”

“…The energy variations of CBM and VBM can be attributed to the variable Ga-O bonds under biaxial compressive or tensile strain, where the σ* anti-bonding and π bonding can bring up and down, respectively, as raising the tensile and compressive strains. 29,36) In order to comprehend the electronic characteristics of Sn GaI and its potential uses in electronics, the transport properties of Sn GaI are determined using the typical DP theory in semiconductors. For the n-type Sn doping in 2D Ga 2 O 3 , we investigate the electron mobility merely here.…”