Anisotropic complex refractive index of β-Ga2O3 bulk and epilayer evaluated by terahertz time-domain spectroscopy

• Published in: Applied physics letters Vol. 118; no. 4
• Main Authors: Agulto, Verdad C., Toya, Kazuhiro, Phan, Thanh Nhat Khoa, Mag-usara, Valynn Katrine, Li, Jiajun, Empizo, Melvin John F., Iwamoto, Toshiyuki, Goto, Ken, Murakami, Hisashi, Kumagai, Yoshinao, Sarukura, Nobuhiko, Yoshimura, Masashi, Nakajima, Makoto
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 25-01-2021
• Subjects: Applied physics; Electric contacts; Gallium oxides; Model accuracy; Refractivity; Spectrum analysis; Terahertz frequencies; Thin films; Time domain analysis
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0031531

Homoepitaxial film and semi-insulating bulk β-Ga2O3 with (001) orientation were studied using terahertz time-domain spectroscopy (THz-TDS) in the frequency region from 0.2 to 3.0 THz parallel to the [100] and [010] directions. The static permittivity of the bulk was determined to be 10.0 and 10.4 along the
a-axis and
b-axis, respectively, and the refractive index values at 0.2 THz are 3.17 and 3.23 for each axis. The electrical resistivity of the epilayer was extracted with good accuracy by employing the Drude–Lorentz model and without the use of electrical contacts. This noninvasive and contact-free material evaluation through THz-TDS proves to be a powerful tool for probing and obtaining various types of information about β-Ga2O3 materials such as bulk and thin films for the development of β-Ga2O3-based device applications.