Heterojunction Diodes Comprised of n-Type Silicon and p-Type Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite

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Heterojunction diodes comprised of p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) and n-type Si, wherein 3 at. % boron-doped UNCD/a-C:H films were deposited on Si substrates by pulsed laser deposition, were electrically studied. The current--voltage ($I$--$V$) characteristics showed the typical rectification action with a leakage current density of $4.7 \times 10^{-5}$ A/cm2 at a reverse voltage of $-1$ V. The carrier transport is expected to be in generation--recombination process accompanied by tunneling at low forward voltages of 0.1--0.5 V, and to be predominantly in tunneling at 0.5--1.0 V, from ideality factors estimated from the forward $I$--$V$ curve. Grain boundaries in the UNCD/a-C:H film might act as centers for tunneling. From the capacitance--voltage measurement, the build-in potential of the heterojunction and an active carrier concentration in the p-type UNCD/a-C:H film were estimated to be 0.6 eV and $1.4 \times 10^{17}$ cm-3, respectively.
2011-03-25