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

Abstract

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.

Terahertz Wave Absorption Property of all Mixed Organic–Inorganic Hybrid Perovskite Thin Film MA(Sn, Pb)(Br, I)3 Fabricated by Sequential Vacuum Evaporation Method

“…Transmission type THz-TDS was utilized to characterize the samples and elucidate their THz-wave absorption properties. ( Nakajima et al, 2008 ; Nakajima et al, 2009 ; Nakajima et al, 2016 ; Jung et al, 2018 ; Ohkoshi et al, 2020 ; Agulto et al, 2021 ; Fitzky et al, 2021 ). Transmittances of the samples were obtained by non-destructive testing and analysis using an Advantest TAS7500 THz spectroscopy system, which allowed the direct measurement of time-domain THz waveforms and the corresponding power spectra at room temperature (22 ± 1°C) and dry air (relative humidity <1.5%) conditions.…”

Characterization of electrical properties of β-Ga2O3 epilayer and bulk GaAs using terahertz time-domain ellipsometry

“…The advancement of terahertz (THz) technology has led to the wide application of THz waves in probing semiconductor properties. In particular, THz time-domain spectroscopy (THz-TDS) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] is established as a nondestructive, noncontact technique to evaluate the electrical properties of semiconductors with good accuracy. For the development of semiconductor devices, it is necessary to characterize the carrier concentration and mobility which are typically measured using conventional electrical characterization methods such as the Hall effect measurement.…”

“…Hence, THz-TDS is advantageous for anisotropic semiconductors. 3) Furthermore, since THz-TDS does not require electrical contacts, there is no need to consider contact resistance, making it practical for investigating new materials. Spatial mapping of electrical properties can also be attained using THz-TDS, 4) which is useful especially because the properties of the sample may vary in-plane.…”

Highly Sensitive Dual-Band Terahertz Metamaterial Absorber for Biomedical Applications: Simulation and Experiment

“…In the THz frequency range, studies were conducted to focus on continuous-wave THz imaging, , THz time-domain spectroscopy, − and THz near-field imaging. , The other topics of research in the terahertz regime are absorbers, − terahertz radiations, − waveguides, − wireless communications, , and sensors. − Research in the THz sensors focuses on discriminating nanoscaled biological or chemical samples as it is possible to measure their structural behavior in this frequency regime. These samples can be sensed and precisely measured by utilizing the extraordinary features of MTMs.…”