Properties of Co-Sputtered $(\text{In}_{\mathrm{X}}\text{Ga}_{(1-\mathrm{X})})_{2}\mathrm{O}_{3}$ Layers Used in CdTe Solar Cells

We recently demonstrated that
$\left(\mathbf{In}_{\mathbf{x}} \mathbf{Ga}_{\boldsymbol{1-}\mathbf{x}}\right)_{\boldsymbol{2}} \mathbf{O}_{\boldsymbol{3}}$
(IGO) alloys have the potential to be high-performing emitters in CdTe based photovoltaic devices, readily producing devices with efficiencies in excess of 16%. Here we present characterization data for the
$(\mathbf{In}_{\mathbf{x}}\mathbf{Ga}_{\boldsymbol{1-}\mathbf{x}})_{\boldsymbol{2}}\mathbf{O}_{\boldsymbol{3}}$
(IGO) films as x was varied from 0 to 1. As grown IGO films exhibited band gaps ranging from 3.3 eV to 4.77 eV and were amorphous and highly resistive. After heating through a temperature profile that would be experienced during CdTe deposition, Hall effect measurements found n-type conductivity and carrier concentrations ranging from
$\boldsymbol{10^{19}}$
to
$\boldsymbol{10^{20}}\ \mathbf{cm}^{\boldsymbol{-3}},$
. The best performing solar cell was fabricated with
$\mathbf{x}\boldsymbol{=0.36}$
, which showed a bandgap of 4.02 eV, a carrier concentration of
$\boldsymbol{2.5} \ \mathbf{x}\ \boldsymbol{10^{19}}\ \mathbf{cm}^{\boldsymbol{-3}}$
, and a mobility of
$\boldsymbol{9.1}\ \mathbf{cm}^{\boldsymbol{2}}/\mathbf{V}.\mathbf{s}$
. PL measurements showed the brightest emission for this same composition.