Abstract ：

Non-equilibrium carrier lifetimes in nitrogen-doped and boron-doped single crystal HPHT diamonds have been investigated using a non-destructive optical method. In this method, a fiber was used to send a probe beam into the double-side polished sample and collect the interference beams reflected from the front and rear surfaces for directly measuring the refractive index change with a spatial resolution of about 10 mu m. Carrier lifetimes at several points in each sample have been investigated, whose relationships with the impurity concentrations have been analyzed. The nitrogen impurity can effectively reduce the carrier lifetime. Fast and slow carrier recombination components have been found in the boron-doped sample, which are caused by the deep traps and the compensated boron impurity, respectively. This investigation method can also provide a scheme for estimating the impurity concentration in diamond with a high spatial resolution. Published by AIP Publishing.

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Abstract ：

The electrical properties, surface morphology and interface characteristics of W/p-diamond contact before and after annealing have been investigated. It is shown that the as-fabricated W/p-diamond contact exhibited non-linear behavior. After annealing at a temperature higher than 400 degrees C, the W/p-diamond contact showed ohmic behaviour. The specific contact resistance of W/p-diamond was 8.2 x 10(-4) Omega.cm(2) after annealing at 500 degrees C for 3 min in a N-2 ambient, which was extracted from fitting the I-V relationship of TLM. It is noted that the RMS roughness increases with the annealing temperature increasing, which could be ascribed to the formation of WOX by the reaction of W and oxygen at high temperature. The XPS measurement showed that the barrier height of the W/p-diamond is 0.45 +/- 0.12 eV after annealing at 500 degrees C. Furthermore, the formation of defects at the W/p-diamond interface, probably created by the formation of tungsten carbide during rapid thermal annealing, should be responsible for the ohmic formation of W/p-diamond after annealing at high temperature. (C) 2018 Elsevier B.V. All rights reserved.

Keyword ：

Barrier height Diamond I-V Ohmic contact TLM XPS

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Abstract ：

Fabrication of dual-termination Schottky barrier diode (SBDDT) by using oxygen-/fluorine-terminated diamond (OT-/FT-diamond) has been carried out on P-/P + diamond. X-ray photoelectron spectroscopy (XPS) measurement was used to determine the chemical composition of OT-/FT-diamond surface treated by ultraviolet ozone and C4F8 plasma, respectively. The barrier heights of Au on OT-/FT-diamond were calculated to be 2.0 +/- 0.12 and 2.39 +/- 0.12 eV, respectively. Au film was patterned on the OT-/FT-diamond as the schottky electrode, and Ti/Au film were deposited on the backside of substrate as ohmic electrode, then a SBDDT was achieved completely. SBDDT exhibits better forward and reverse I-V characteristics based on the optimum OT-/FT-diamond (W-O/W-F) area ratio 0.2, which illustrates that the combination of dual surface termination is an efficient way to optimize the performance of diamond SBD.

Keyword ：

Barrier height OT-/FT-diamond SBD Surface treatment XPS

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Abstract ：

To measure the temporal width and the intensity evolution versus time of a MeV gamma pulse generated by a Compton Scatter Source, a time-space conversion method is proposed. This design is based on the consideration that the temporal length of the MeV pulse is proportional to the spatial length of the pulse in a certain semiconductor. The spatial length and the intensity evolution versus time of the MeV pulse can be obtained by recording the region of the refractive index change that is induced by the MeV pulse. The simulation suggests that the equivalent temporal spread of a mono-energy MeV delta pulse in a bulk semiconductor is on the order of picoseconds and does not vary significantly with photon energy and material type. According to our analysis, the excess carrier generation time, excess carrier diffusion and recombination do not significantly influence the temporal resolution of this method. The temporal response of the refractive index change to a MeV pulse is also fast enough to meet the measurement requirements. The signal generation process for measuring a 10-ps MeV pulse with a 200-fs probe beam is analyzed, revealing that the transverse size of the MeV pulse does not influence the temporal resolution of this method. (C) 2018 Elsevier B.V. All rights reserved.

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Abstract ：

Self-powered ultraviolet photodetectors based on n-GaN and p-NiO were fabricated through thermal oxidation. The transparent NiO was mainly dominated by [111] texture with an optical band gap of approximately 3.69 eV. Compared with the conventional Ni/GaN photodetector, the p-NiO/GaN heterostructure photodetector possess a larger turn-on voltage and a smaller dark current because of the relatively higher effective barrier height. At an external bias of 0 V, the photo responsivity and the UV to visible rejection ratio of the NiO/GaN photodetector are enhanced to 0.15 A/W and 406, respectively. The improvement in UV photodetector performance is attributed to that the depletion region in NiO/GaN heterostructure can effectively eliminate the trapping charge carriers at the metal/semiconductor interface. The high-performance NiO/GaN photodetectors without driving power are potential for portable UV detectors application.

Keyword ：

GaN P-NiO electrode Self-powered Ultraviolet photodetector

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