研究目的
Investigating the generation of terahertz waves by photoconductive antennas based on epitaxial films of In0.5Ga0.5As on GaAs substrates with different crystallographic orientations and growth conditions.
研究成果
The study demonstrates that low-temperature grown InGaAs films on GaAs wafers with (1 1 1)A orientation are promising materials for THz wave generation by photoconductive antennas. The THz generation is more effective in films grown on (1 1 1)A substrates compared to (1 0 0) substrates, and the intensity of the THz pulse is higher for films with lower Hall electron mobility. The findings suggest that the substrate orientation and growth conditions significantly influence the efficiency of THz wave generation.
研究不足
The study is limited by the small resistance of the epitaxial film between the electrodes, which restricts the operating voltage range. Additionally, the real spectrum of the antenna-emitter may be wider than the measured 2 THz due to the decline in spectral sensitivity of the antenna-receiver.
1：Experimental Design and Method Selection:
The study utilized terahertz time-domain spectroscopy to analyze THz wave generation by photoconductive antennas fabricated on In
2：5Ga5As films grown by molecular beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1)A orientations. The antennas were excited by an Er3+-fiber laser at 56 μm wavelength in two regimes:
with pulse durations of 2.5 ps or 100 fs.
3：5 ps or 100 fs.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Samples were grown by molecular-beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1)A orientations, utilizing step-graded InxGa1?xAs metamorphic buffer. The active layers were grown at either high temperature (450 °C) or low temperature (200 °C) and were either uniformly Si-doped or unintentionally doped.
4：List of Experimental Equipment and Materials:
The experimental setup included an Er3+-fiber laser, photoconductive antennas, a delay line, an optical chopper, a lock-in amplifier, and a hemispherical Si-lens for THz radiation collimation.
5：Experimental Procedures and Operational Workflow:
The laser beam was divided into two parts, with one part focused on the THz detector and the other part used to excite the antenna under investigation. THz radiation was collimated and focused onto a receiving photoconductive antenna, with electrical signals amplified and detected using a lock-in amplifier.
6：Data Analysis Methods:
The temporal dynamics of the electric field were measured, and fast Fourier transform (FFT) was used to analyze the frequency domains of the THz radiation pulses.
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