Abstract
To investigate the effects of the pixel sizes and the electrode structures on the performance of Ge-based terahertz (THz) photoconductive detectors, vertical structure Ge:Ga detectors with different structure parameters were fabricated. The characteristics of the detectors were investigated at 4.2 K, including the spectral response, blackbody response (Rbb), dark current density-voltage characters, and noise equivalent power (NEP). The detector with the pixel radius of 400 μm and the top electrode of the ring structure showed the best performance. The spectral response band of this detector was about 20–180 μm. The Rbb of this detector reached as high as 0.92 A/W, and the NEP reached 5.4 × 10−13 W/ at 0.5 V. Compared with the detector with a pixel radius of 1000 μm and the top electrode of the spot structure, the Rbb increased nearly six times, and the NEP decreased nearly 12 times. This is due to the fact that the optimized parameters increased the equivalent electric field of the detector. This work provides a route for future research into large-scale array Ge-based THz detectors.
Highlights
Terahertz (THz) detection is useful for many practical applications, such as astronomical observations, nondestructive testing, and biomedical treatment [1–3]
The Ge-based impurity detector has been developed for many years, there is still a large gap compared with other terahertz detectors in terms of array scale, performance, and maturity [14,15], due to many fabrication difficulties and problems
The current density of the detector increased as the pixel size decreased
Summary
Terahertz (THz) detection is useful for many practical applications, such as astronomical observations, nondestructive testing, and biomedical treatment [1–3]. The impurity band detector as a typical extrinsic photoconductive THz detector is widely studied for its high sensitivity, wide spectrum, and fast response, which realizes detection by constructing an impurity band in a semiconductor energy gap and causing electrons to transition between the impurity band and the conduction band or valence band [4–6]. It has been developed widely with a cutoff wavelength of nearly 200 μm, and it has already been used in astronomical observations such as the ASTRO-F project and the Spitzer Space Telescope [11–13]. The Ge-based impurity detector has been developed for many years, there is still a large gap compared with other terahertz detectors in terms of array scale, performance, and maturity [14,15], due to many fabrication difficulties and problems.
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