UV and visible photoconductivity of undoped diamond films: morphology and related electrical transport phenomena

UV and visible photoconductivity and electrical features of undoped diamond thin films grown by microwave plasma-assisted chemical vapour deposition (MP-CVD) on silicon and copper substrates are studied. The results are correlated with morphology properties analysed by atomic force microscopy (AFM) and micro-Raman. The photoconductivity presents several bands from 1.8 to 3.8 eV that are dependent on the substrate used to grow the samples in spite of some common bands observed. The J-V curve tin DC) in samples grown on Si has a rectifier behaviour (Schottky emission) in opposition to the samples grown on Cu that have no rectification (SCLC conduction). With these results we can conclude that diamond based optoelectronic devices behaviour is controlled by two kinds of structural defects localized in microcrystal and in its boundaries. A general structure model for the optoelectronic behaviour is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

Polycrystalline diamond thin film as wide bandgap material: the optoelectronic behaviour and the relationship with the structure

In this work metal - Microwave Plasma CVD diamond Schottky devices were studied. The current density vs. applied voltage reveals rectification ratios up to 10(4) at \ +/- 2V \. Under illumination an inversion and increase of the rectification is observed. The carrier density is 10(15) cm(-3) and the ideality factors near 1.5. The dark current vs. temperature shows that below 150 K the bulk transport is controlled by a hopping process with a density of defects of 10(16) cm(-3). For higher temperatures an extrinsic ionisation with activation energy of 0.3 eV takes place. The correlation with the polycrystalline nature of the samples is focused.