• A Azam

      Articles written in Pramana – Journal of Physics

    • Experimental analysis of current conduction through thermally grown SiO2 on thick epitaxial 4H-SiC employing Poole–Frenkel mechanism

      Sanjeev K Gupta A Azam J Akhtar

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      Electrical properties of SiO2 grown on the Si-face of the epitaxial 4H-SiC substrate by wet thermal oxidation technique have been experimentally investigated in metal oxide–silicon carbide (MOSiC) structure with varying oxide thicknesses employing Poole–Frenkel (P–F) conduction mechanism. The quality of SiO2 with increasing thickness in MOSiC structure has been analysed on the basis of variation in multiple oxide traps due to effective P–F conduction range. Validity of Poole–Frenkel conduction is established quantitatively employing electric field and the oxide thickness using forward $I–V$ characteristics across MOSiC structures. From P–F conduction plot (ln($J/E$) vs. $E^{1/2}$), it is revealed that Poole–Frenkel conduction retains its validation after a fixed electric field range. The experimental methodology adopted is useful for the characterization of oxide films grown on 4H-SiC substrate.

    • Variation of interface trap level charge density within the bandgap of 4H-SiC with varying oxide thickness

      Sanjeev K Gupta A Azam J Akhtar

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      Interfacial characteristics of metal oxide-silicon carbide (MOSiC) structure with different thickness of SiO2, thermally grown in steam ambient on Si-face of 4H-SiC (0 0 0 1) substrate were investigated. Variations in interface trapped level density ($D_{\text{it}}$) was systematically studied employing high-low (H-L) frequency $C–V$ method. It was found that the distribution of $D_{\text{it}}$ within the bandgap of 4H-SiC varied with oxide thickness. The calculated $D_{\text{it}}$ value near the midgap of 4H-SiC remained almost stable for all oxide thicknesses in the range of $10^9 –10^{10}$ cm-2 eV-1. The $D_{\text{it}}$ near the conduction band edge had been found to be of the order of 1011 cm-2 eV-1 for thicker oxides and for thinner oxides $D_{\text{it}}$ was found to be the range of 1010 cm-2 eV-1. The process had direct relevance in the fabrication of MOS-based device structures.

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