Low Pressure Chemical Vapor Deposition of Aluminum-Doped Zinc Oxide for Transparent Conducting Electrodes

We carried out comprehensive studies on structural, optical, and electrical properties of aluminum-doped zinc oxide (AZO) films deposited by low pressure chemical vapor deposition (LP-CVD). The growth rates of LP-CVD AZO films increased slightly with Al doping. In addition, the resistivity was strongly dependent on the carrier electron concentration, also correlated with optical band gap and work function. All the AZO films exhibited high optical transmittance of >80% in the visible range of 400–700 nm and high work function of >4.6 eV regardless of the Al content. For the comparative studies on the electrical properties as gate electrodes, metal-oxide-semiconductor (MOS) capacitors were prepared by LP-CVD AZO and sputtered ITO as gates. The AZO gate showed higher dielectric constant (k = 8.8), lower interface state (Dit = 1.5 × 1011 cm−2eV−1), effective oxide charge (Qeff = 4.8 × 1011), and leakage current density (2.3 × 10−8 A/cm2 at −1 MV/cm) than the ITO gate (k = 8.5, Dit = 3 × 1011 cm−2eV−1, Qeff = 1.4 × 1012 cm−2 and leakage current density = 5.7 × 10−8 A/cm2 at −1 MV/cm, respectively).