III-V compound detectors for CO 2 DIAL measurements

Abstract

Profiling of atmospheric carbon dioxide (CO 2 ) is important for understanding the natural carbon cycle on Earth and its influence on global warming and climate change. Differential absorption lidar is a powerful remote sensing technique used for profiling and monitoring atmospheric constituents. Recently there has been an interest to apply this technique, at the 2 µm wavelength, for investigating atmospheric CO 2 . This drives the need for high quality detectors at this wavelength. Although 2 µm detectors are commercially available, the quest for a better detector is still on. The detector performance, regarding quantum efficiency, gain and associated noise, affects the DIAL signal-to-noise ratio and background signal, thereby influencing the instrument sensitivity and dynamic range. Detectors based on the III-V based compound materials shows a strong potential for such application.In this paper the detector requirements for a long range CO 2 DIAL profiles will be discussed. These requirements were compared to newly developed III-V compound infrared detectors. The performance of ternary InGaSb pn junction devices will be presented using different substrates, as well as quaternary InGaAsSb npn structure. The performance study was based on experimental characterization of the devices dark current, spectral response, gain and noise. The final results are compared to the current state-of-the-art InGaAs technology. Npn phototransistor structure showed the best performance, regarding the internal gain and therefore the device signal-to-noise ratio. 2-µm detectivity as high as 3.

RECENT DEVELOPMENT OF SB-BASED PHOTOTRANSISTORS IN THE 0.9- TO 2.2-μM WAVELENGTH RANGE FOR APPLICATIONS TO LASER REMOTE SENSING

“…3. Comparison of spectral response measurements for commercial and custom-designed detectors 32 Figure 4 shows the dark current variation with bias voltage for the different detectors, obtained by measuring the current-voltage characteristics of the device in a dark condition at a temperature of 20 o C 32 . The InGaAs (2.3-µm) detector (G5852) indicated the lowest dark current even at higher bias voltages.…”

Quantum-dot Infrared Photodetector Fabricated by Pulsed Laser Deposition Technique

“…Silver epoxy was used to mount the QD detector sample on an aluminum sample holder and to fix the connecting wires to the Al pads. Figure 5 shows a schematic of the characterization setup [11]. The setup consists mainly of optical, electrical and mechanical sections.…”

Calculations of the temperature and alloy composition effects on the optical properties of AlxGa1−xAsySb1−y and GaxIn1−xAsySb1−y in the spectral range 0.5–6 eV

“…A detailed knowledge of their optical properties is essential for the design and fabrication of heterojunction photodetectors, thermophotovoltaic cells, infrared light-emitting diodes, fiber optics, and injection lasers. [1][2][3] The optical response of a material in terms of the incident radiation frequency ͑͒ is fully described by the complex dielectric function ͑͒ = 1 ͑͒ + i 2 ͑͒, where the real and imaginary parts are related by the Kramers-Kronig transformation. 1 The dielectric function is experimentally determined using various techniques, such as spectroscopic ellipsometry, reflectance measurements, and electron-energyloss spectroscopy.…”