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

Abstract

We have investigated commercially available photodiodes and also recent developed Sb -based phototransistors in order to compare their performances for applications to laser remote sensing. A custom-designed phototransistor in the 0.9- to 2.2-μm wavelength range has been developed at AstroPower and characterized at NASA Langley's Detector Characterization Laboratory. The phototransistor's performance greatly exceeds the previously reported results at this wavelength range in the literature. The detector testing included spectral response, dark current and noise measurements. Spectral response measurements were carried out to determine the responsivity at 2-μm wavelength at different bias voltages with fixed temperature; and different temperatures with fixed bias voltage. Current versus voltage characteristics were also recorded at different temperatures. Results show high responsivity of 2650 AIW corresponding to an internal gain of three orders of magnitude, and high detectivity (D*) of 3.9×1011 cm.Hz 1/2/ W that is equivalent to a noise-equivalent-power of 4.6×10-14 W/Hz 1/2 (-4.0 V @ -20°C) with a light collecting area diameter of 200-μm. It appears that this recently developed 2-μm phototransistor's performances such as responsivity, detectivity, and gain are improved significantly as compared to the previously published APD and SAM APD using similar materials. These detectors are considered as phototransistors based-on their structures and performance characteristics and may have great potential for high sensitivity differential absorption lidar (DIAL) measurements of carbon dioxide and water vapor at 2.05-μm and 1.9-μm, respectively.

Infrared detector activities at NASA Langley Research Center

“…Figure 1 shows the responsivity variation with wavelength in the 0.6-to 2.4-μm range at different collector-emitter voltages and temperatures of such a device [11]. The responsivity is strongly dependent on wavelength, temperature, and bias voltage.…”

“…In this context, it is necessary to explore alternative material systems, which can absorb radiation in the 1.0-to 2.5-μm range and are compatible with general requirements of a low-noise detector. InGaAsSb/AlGaAsSb heterostructures are very suitable for this application, and single-element HPTs based on these heterostructures demonstrated record responsivitites [3,4,[8][9][10][11][12][13][14].…”

“…These devices have been characterized at NASA LaRC and encouraging results have been obtained, including high responsivity, high detectivity, and relatively low NEP [3,4,[8][9][10][11][12][13][14]. Development of large-format Sb-based phototransistor FPA will enhance the capability of space-based active and passive remote sensing imaging systems and enable major advances in Astronomical, Earth, and planetary instruments.…”