Extracting the Complex Refractive Index of an Ultrathin Layer at Terahertz Frequencies With no Prior Knowledge of Substrate Absorption Loss

Carnio, Brett N.; Attiaoui, Anis; Assali, Simone; Moutanabbir, Oussama; Elezzabi, A. Y.

doi:10.1109/tthz.2021.3140196

IEEE Trans. THz Sci. Technol.

2022

DOI: 10.1109/tthz.2021.3140196

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Extracting the Complex Refractive Index of an Ultrathin Layer at Terahertz Frequencies With no Prior Knowledge of Substrate Absorption Loss

Brett N. Carnio

Anis Attiaoui²,

Simone Assali³

et al.

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Cited by 2 publications

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Dopant profiling of ion-implanted GaAs by terahertz time-domain spectroscopy

Sahoo

Hong

et al. 2023

Journal of Applied Physics

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We investigate terahertz time-domain spectroscopy (THz-TDS) as a non-destructive and non-contact technique for depth profiling of dopants in semiconductors. THz temporal waveforms transmitted through silicon-ion-implanted semi-insulating gallium arsenide substrates, as-implanted or post-annealed by rapid thermal annealing, were analyzed by assuming a multi-layered Gaussian refractive index profile in the ∼sub-micrometer-thick implantation region. The implantation energy and dosages in this work were 200 KeV, 1014, 5 × 1014, and 1015 ions/cm2, respectively. The average values of real ( n) and imaginary ( κ) parts of refractive indices of an as-implanted sample in the depth range of 0–800 nm are 5.8 and 0.7, respectively, at 0.5 THz and are 6.2 and 0.2, respectively, at 1 THz. On the other hand, the refractive index profile of the post-annealed samples displays a prominent Gaussian-like form, and peak refractive indices ( n ∼ 25 and κ ∼ 32.7 at 0.5 THz and n, κ ∼17 at 1 THz) were found to be at the depth of 210 nm. Reconstructed dopant profiles in as-implanted, implanted, and post-annealed substrates were found to be in good agreement with measurements by secondary ion mass spectroscopy as well as simulation by the Monte Carlo method. We were also able to determine accurately the projected range ( Rp), straggle ( Rs), and concentration of dopants by the analysis of THz-TDS data. The spatial resolution, along the depth direction, of the THz-TDS technique for depth profiling of dopants was estimated to be as small as 8-nm. This work suggests the feasibility of using THz-TDS for nondestructive and non-contact diagnostics for profiling dopants in semiconductors.

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Dopant profiling of ion-implanted GaAs by terahertz time-domain spectroscopy

Sahoo

Hong

et al. 2023

Journal of Applied Physics

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All-thin film nano-optoelectronic p-GeSn/i-GeSn/n-GeBi heterojunction for near-infrared photodetection and terahertz modulation

Zhang,

Zheng,

Liao

et al. 2024

APL Photonics

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High-performance alloy thin films and large-sized thin film wafers for infrared applications are the focus of international researchers. In this study, doped Ge1−xSnx and Ge1−yBiy semiconductor alloy films were grown on a 5-in. silicon (Si) wafer using high-quality Ge films as buffer layers. An efficient technique is presented to reduce the dark current density of near-infrared photoelectric devices. By using boron for p-type doping in Ge1−xSnx films and bismuth (Bi) for n-type doping in Ge1−yBiy films, an all-thin film planar nano-p-i-n optoelectronic device with the structure n-Ge1−yBiy/i-GeSn/p-Ge1−xSnx/Ge buffer/Si substrate has been successfully fabricated. The photoelectric performance of the device was tested, and it was found that the insertion of p-Ge1−xSnx/Ge films reduced the dark current density by 1–2 orders of magnitude. The maximum photoresponsivity reached up to 0.8 A/W, and the infrared photocurrent density ranged from 904 to 935 μA/cm2 under a +1 V bias voltage. Furthermore, the device is capable of modulating a terahertz wave using a voltage signal with a modulation bandwidth of 1.2 THz and a modulation depth of ∼83%, while the modulation rate is 0.5 MHz. This not only provides a clear demonstration of how doped alloy films and the development of nano-p-i-n heterojunctions will improve photoelectric devices’ performance in the near-infrared and terahertz bands, but it also raises the possibility of optoelectronic interconnection applications being achieved through a single device.

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Extracting the Complex Refractive Index of an Ultrathin Layer at Terahertz Frequencies With no Prior Knowledge of Substrate Absorption Loss

Cited by 2 publications

References 30 publications

Dopant profiling of ion-implanted GaAs by terahertz time-domain spectroscopy

Dopant profiling of ion-implanted GaAs by terahertz time-domain spectroscopy

All-thin film nano-optoelectronic p-GeSn/i-GeSn/n-GeBi heterojunction for near-infrared photodetection and terahertz modulation

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