Low-Frequency Noise of nc-Si:H/c-Si Heterojunction Diodes

Abstract

Low-frequency noise (LFN) measurements were performed on hydrogenated nanocrystalline silicon (nc-Si:H)/crystalline-silicon heterojunction diodes for the forward- and reverse-biased currents <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> . The 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γ</sup> noise with γ ~ 1.3 (for low <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> ) or 0.6 (for high <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> ) was observed to dominate the LFN, and the noise power spectral density <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Si</i> showed a power-law behavior ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Si</i> ~ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</sup> , where α ~ 2). This quadratic behavior may indicate the 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γ</sup> noise to stem from the carrier number fluctuations mediated by deep trap states (for γ ~ 1.3) or band tail states (for γ ~ 0.6) of nc-Si:H. Also, the band tail width of nc-Si:H was estimated to be ~ 65 meV.