Enhanced Electron Mobility Due to Dopant‐Defect Pairing in Conductive ZnMgO

Abstract

The increase of the band gap in Zn1‐xMgxO alloys with added Mg facilitates tunable control of the conduction band alignment and the Fermi‐level position in oxide‐heterostructures. However, the maximal conductivity achievable by doping decreases considerably at higher Mg compositions, which limits practical application as a wide‐gap transparent conductive oxide. In this work, first‐principles calculations and material synthesis and characterization are combined to show that the leading cause of the conductivity decrease is the increased formation of acceptor‐like compensating intrinsic defects, such as zinc vacancies (VZn), which reduce the free electron concentration and decrease the mobility through ionized impurity scattering. Following the expectation that non‐equilibrium deposition techniques should create a more random distribution of oppositely charged dopants and defects compared to the thermodynamic limit, the paring between dopant GaZn and intrinsic defects VZn is studied as a means to reduce the ionized impurity scattering. Indeed, the post‐deposition annealing of Ga‐doped Zn0.7Mg0.3O films grown by pulsed laser deposition increases the mobility by 50% resulting in a conductivity as high as σ = 475 S cm‐1.

Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells

“…Since the Ga:(Zn,Mg)O were found to be highly doped, an approximation for degenerate semiconductor was used as seen in Equation 2 to calculate CBM. [52] The effective mass m*/m e of ZnO was taken as 0.39 and that of Zn 1-x Mg x O for different x was derived using linear variation (d/dx) of Mg composition (x) obtained from other literature [53] as shown in following equations (4) The difference between the experimental and theoretical CBM position at lower Mg concentration ( Fig. 7) may be related to the very high doping of the material.…”

Design of Semiconducting TetrahedralMn1−xZnxOAlloys and Their Application to Solar Water Splitting

“…Summarizing the analysis of small-polaron formation and self-trapping, we expect [44]. Experimentally, we attempted n-type doping by Gallium, which is known as an efficient dopant in ZnO and in Zn 1−x Mg x O alloys [45]. [20], we determined the electrical conductivity by performing combinatorial, spatially resolved fourpoint probe measurements of the sheet resistance.…”

Improving electron transport in Ga-doped Zn0.7Mg0.3O, a wide-gap band-edge-energy-tunable transparent conducting oxide

“…However, the observed substantial decrease in electrical conductivity, from Gmax "" 3,000 S/cm for x = 0 to Gmax "" 300 S/cm for x = 0.3 for comparable doping levels, has limited its use [1][2][3][4]. Using combined material synthesis, electrical transport measurements, and first-principles theory, we demonstrate that for gallium (Ga)-doped Zn0 7 Mgo30, intrinsic acceptors, such as zinc vacancies (V Zn) , reduce the electrical conductivity by both trapping electrons and increasing the ionized impurity scattering [5].…”