Electronic and structural characteristics of a polycrystalline IrO₂:Li/(100)-oriented Si pn heterojunction

Achieving optimal band alignment and efficient p-type conductivity is a critical challenge for the heterogeneous integration of wide bandgap materials onto silicon (Si), a key step in revolutionizing next-generation integrated circuits (ICs). In this work, we report what we believe to be the first investigation of the heterojunction formed by pulsed laser deposition (PLD) growth of lithium-doped iridium oxide (IrO₂:Li) on (100)-oriented Si. The IrO₂:Li films exhibit a polycrystalline structure with a preferred (200) out-of-plane orientation, as confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Monochromated electron energy loss spectroscopy (EELS) measurements revealed an electronic bandgap of 2.90 eV for the IrO₂:Li film, which is corroborated by photoluminescence (PL) measurements and consistent with prior work on undoped IrO₂. Electrical characterization demonstrated p-type conductivity with a high carrier concentration, comparable to that of epitaxial IrO₂ films. The valence and conduction band offsets at the IrO₂:Li/Si heterointerface were determined to be 0.76 ± 0.10 and 2.54 ± 0.10 eV, respectively, using high-resolution X-ray photoelectron spectroscopy (HRXPS), indicating a type-II (staggered) band alignment. The combination of wide bandgap, p-type conductivity, and favorable band alignment with Si makes PLD-grown IrO₂:Li a promising candidate for future optoelectronic and power devices integrated with Si technology.