Chemical, optical, and electrical characterization of Ga2O3 thin films grown by plasma-enhanced atomic layer deposition

• Published in: Current applied physics Vol. 19; no. 2; pp. 72 - 81
• Main Authors: Li, Xing, Lu, Hong-Liang, Ma, Hong-Ping, Yang, Jian-Guo, Chen, Jin-Xin, Huang, Wei, Guo, Qixin, Feng, Ji-Jun, Zhang, David Wei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2019; 한국물리학회
• Subjects: ALD; Ga2O3; Thin films; Wide band gap; 물리학; Thin films; Ga2O3; ALD; Wide band gap
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2018.11.013

Thin Ga2O3 films were grown on Si (100) using trimethylgallium (TMG) and oxygen as the precursors through plasma-enhanced atomic layer deposition. The depositions were made over a temperature range of 80–250 °C with a growth per cycle of around 0.07 nm/cycle. Surface self-saturating growth was obtained with TMG pulse time ≥20 ms at a temperature of 150 °C. The root mean square surface roughness of the obtained Ga2O3 films increased from 0.1 nm to 0.3 nm with increasing the growth temperature. Moreover, the x-ray photoelectron spectroscopy analysis indicated that the obtained film was Ga-rich with the chemical oxidation states Ga3+ and Ga1+, and no carbon contamination was detected in the films after Ar+ sputtering. The electron density of films measured by x-ray reflectivity varied with the growth temperature, increasing from 4.72 to 5.80 g/cm3. The transmittance of Ga2O3 film deposited on a quartz substrate was obtained through ultraviolet visible (UV–Vis) spectroscopy. An obvious absorption in the deep UV region was demonstrated with a wide band gap of 4.6–4.8 eV. The spectroscopic ellipsometry analysis indicated that the average refractive index of the Ga2O3 film was 1.91 at 632.8 nm and increased with the growth temperature due to the dense structure of the films. Finally, the I-V and C-V characteristics proved that the Ga2O3 films prepared in this work had a low leakage current of 7.2 × 10−11 A/cm2 at 1.0 MV/cm and a high permittivity of 11.9, suitable to be gate dielectric.