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Journal of Physical Studies 7(4), 419–425 (2003)
DOI: https://doi.org/10.30970/jps.07.419 THE INFLUENCE OF AMMONIA VAPORS ON THE SURFACE CURRENT IN p–n JUNCTIONS ON III–V SEMICONDUCTORSO. Ptaschchenko, O. Artemenko, F. Ptashchenko1
I. I. Mechnikov National University of Odessa,
2 Dvoryanska Str., Odessa, 65100, Ukraine |
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The influence of ammonia vapors on I-V characteristics of the forward and reverse currents in AlGaAs-GaAs laser heterostructures as well as in GaAs $p$-$n$ structures was studied. The forward- and reverse currents are strongly enhanced in the ammonia atmosphere. I-V curves of the excess surface current (ESC) caused by the adsorption of ammonia molecules are linear. The slope of these curves linearly depends on the ammonia partial pressure over the range 10$^{{\rm 2}}$-10$^{{\rm 4}}$Pа. The results are interpreted in terms of forming a conducting surface cannel caused by the electrical field of ammonia ions located on the surface of the natural oxide. The ionizing NH$_{{\rm 3}}$ molecules inject electrons in this channel. The change of I-V curves of $p$-$n$ structures in ammonia vapors can be utilized for the creation of an ammonia sensor. The mostly sensitive to ammonia vapors (up to 1$\cdot$10$^{-8}$А$\cdot$Pа$^{-1}$V$^{-1})$ were GaAs $p$-$n$ junctions with a polished lateral surface. The kinetics of the ESC rise and its decay under varying gas atmosphere was measured in the temperature range 290-330 К. The rise- and decay time of ESC in laser heterostructures was of 20-60 s and 2-8 s, respectively. The rise of ESC in the GaAs $p$-$n$ junctions with a polished lateral surface has two stages; the second of them is very long, of 1000 s. The decay time of ESC of these structures is of the same order of value, as for laser heterostructures. The kinetics of the current rise and its decay, caused by adsorption and desorption of NH$_{3}$ molecules, suggests that the GaAs $p$-$n$ junctions with a polished lateral surface have surface recombination centers with a small capture cross-section for electrons. These centers have a potential barrier of $Δ E=0.52$ еV for the capture of charge carriers.
PACS number(s): 73.20.Hb, 73.25.+i.