Broadband infrared detectors

Year: 2003

Jiří Zelinka, MSc.; Zdislava Podvalová, MSc.

Detectors of infrared radiation come, in essence, in two varieties, namely photonic (based on semiconductors) and pyroelectric (realized with ferroelectric materials). Photonic detectors, by their nature narrow-band, are mostly used in optical communications and for rapid optical signals processing. Pyroelectric infrared detectors usually cover the broad wavelength range 2 – 25m which is of advantage for numerous applications such as alarm systems, contactless temperature measurements, and scientific tasks (e.g. FTIR spectroscopy and exact calorimetry). They also proved to be useful in gas detectors for ecology and chemistry as well as in military applications such as infrared tracking systems and night vision.

In the Institute of Radio Engineering and Electronics, Academy of Sciences of the Czech Republic, novel ferroelectric monocrystals on the basis of hybrid triglycinium phosphate doped with L-alanine and Pt(IV) ions (LATGS/Pt(IV) for short) have been prepared [1, 2]. They exhibit elevated pyroelectric coefficient values and superior homogeneity. The Pt-glycine complex secures internal polarization Eb values suitable for construction of broadband infrared detectors. Interest to study properties of these crystals was manifested by workers of the Physical Laboratory of the University of Alabama, USA, an institution with more than thirty years of experience with warfare applications of ferroelectric materials.

On the basis of LATGS/Pt(IV) monocrystals, the pyroelectric detectors were assembled in cooperation with the TESLA Blatná Company. The detectors possess high sensitivity values that compare very favourably with products of laboratories abroad [3-5]. The detector wafers have been designed to fit into the normalized TO5 housing so as to make the detectors friendly for the envisaged mass production. The devices were thorougly characterised and care was taken to optimize the system of absorption electrodes. The nearest applications of the detectors are expected to be in the field of gas sensors for ecology and chemistry.

1. Novotný, J., Zelinka, J., Podvalová, Z.: Catalysed growth of doped TGS single crystals for infrared applications. Proceedings of SPIE. Vol 4710, 704. Int. Conf. Thermosense XXIV, Orlando USA 2002.
2. Novotný, J., Zelinka, J.: Characterisation of LATGS and LADTGS Single Crystals Doped with Pt(II) and Pt(IV) Ions for Infrared Applications. Int. Congress “Euromat 2003”, Poster,1-5.9. Lausanne 2003.
3. Novotný, J., Podvalová, Z., Zelinka, J.: Growth of Triglycine Sulfate Single Crystals Doped with Pt(IV) and L-alanin. Crystal Growth and Design 3: 393-395 (2003).
4. Novotný, J. Zelinka, J., Franc, J.: Technology of Infrared Detectors Preparation on the Basis of LATGS/Pt(IV) and LADTGS/Pt(II) Single Crystals. Mezinár. konf. Applied Electronics 2003, Plzeň, 152-156 (2003).
5. Novotný, J., Březina, B., Zelinka J.: Growth and characterization of TGS and DTGD single crystals doped with Pt(II), Pt(IV) and L-alanine. Crystal Research and Technology (in print, 2003).