Fabrication of the GaAs based terahertz photoconductors and the photometer for Tera-GATE

Kentaroh Watanabe; Kyouhei Yamashita; Hirokazu Kataza; Takafumi Kamizuka; Takehiko Wada; Moriaki Wakaki; Osamu Abe; Hiroshi Murakami

doi:10.1117/12.789143

21 July 2008 Fabrication of the GaAs based terahertz photoconductors and the photometer for Tera-GATE

Kentaroh Watanabe, Kyouhei Yamashita, Hirokazu Kataza, Takafumi Kamizuka, Takehiko Wada, Moriaki Wakaki, Osamu Abe, Hiroshi Murakami

Author Affiliations +

Proceedings Volume 7020, Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV; 702020 (2008) https://doi.org/10.1117/12.789143
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

The present status of the development of an extrinsic photoconductor based on a high-purity GaAs is reported. This photoconductor utilizing the shallow donor levels in GaAs and is highly sensitive for incident terahertz photons in the wavelength range 150 to 300 micron. The n-type GaAs crystal has been growth by liquid phase epitaxial (LPE) method, which is suitable to obtain thick and high-purity GaAs. The impurity concentration in GaAs layer has been decreased to the order of 10¹³ atoms/cm^-3. By doping the donors lightly in the LPE growth process, C/Si, (background doped) Se and Te doped GaAs layers has been fabricated. The GaAs photoconductors using these crystals are sensitive in longer wavelength region than Ge:Ga photoconductors used in the past far-infrared astronomical observations. The most sensitive detector is obtained with C or Si background doped GaAs, of which NEP is reached to 3×10^-16 W/Hz^0.5 at the temperature of 1.5 K, at 290 micron, the peak of its responsivity spectrum. A balloon-borne telescope utilizing our GaAs photoconductors, Tera-GATE (THz observation with GaAs photoconductors and a balloon-borne Telescope) is now under development. The Tera-GATE is a 69 cm diameter telescope. On its focal plane, a photoconductor array with Winston cone has 2-mm entrance aperture and leads the incident photons to a cavity where 0.5-mm size photoconductor is installed. Measured optical efficiency of the cone/cavity system is in an acceptable range ~40 percent.

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Kentaroh Watanabe, Kyouhei Yamashita, Hirokazu Kataza, Takafumi Kamizuka, Takehiko Wada, Moriaki Wakaki, Osamu Abe, and Hiroshi Murakami "Fabrication of the GaAs based terahertz photoconductors and the photometer for Tera-GATE", Proc. SPIE 7020, Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV, 702020 (21 July 2008); https://doi.org/10.1117/12.789143

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