In this study, we present the fabrication and characterization of ZnO nanorods (NRs) grown on p-Si, gold (Au) and nickel (Ni) coated on Si wafer, indium tin oxide (ITO), and quartz substrates. The aqueous chemical growth method is used for the vertical growth of ZnO NRs on multiple substrates. The samples are characterized with scanning electron microscope and energy dispersive X-ray spectroscopy to probe into the growth, alignment, density, diameter, and length of ZnO NRs on multiple substrates. It is found that under same conditions, like growth temperature, growth time, and solution concentration, ZnO NRs on ITO and quartz have same length but comparatively larger diameter than on other samples. The effects of growth time on the diameter and length of ZnO NRs are also explored. All the samples are characterized with probe station to look at the current-voltage (I-V) behavior of ZnO NRs on multiple substrates. It is found that ZnO NRs on p-Si show a simple p-n heterojunction diode like behavior. ZnO NRs grown on Au- and Ni-coated Si wafers show Schottky I-V characteristic behaviors while ZnO NRs on ITO show a simple ohmic I-V response with comparatively higher level of current. Finally, the I-V response of ZnO NRs on p-Si is also studied under ultraviolet illumination. Because of the photo-generated carriers in ZnO, the sample shows higher level of current upon illumination.

In this study, we present a GaAs varactor diode with a hyperabrupt junction for the enhancement of breakdown voltage and capacitance variation in a reverse bias state. The hyperabrupt doping profile in the n-type active layer is prepared in a controlled nonlinear manner, with the density of the dopants increasing towards the Schottky junction. The hyperabrupt GaAs varactor diode is fabricated and characterized for breakdown voltage and capacitance over the electric field, induced by an applied reverse bias voltage. A reduced value of the electric field is observed owing to the nonlinear behavior of the electric field at the hyperabrupt junction, although the device has a larger doping density at the Schottky junction. Furthermore, the capacitance ratio of the hyperabrupt junction diode is also improved. Variation in the device capacitance is affected by variation in the depletion region across the junction. Technology CAD is used to understand the experimental phenomena by considering the magnitude of charge density as a function of the doping profile. A higher breakdown voltage and greater capacitance modulation are shown in the hyperabrupt junction diode compared to the uniform junction diode.

We investigate the performance of hyperabrupt doping profile based GaAs varactor diodes. Epitaxially grown GaAs nn+ devices, having an intentionally graded n‐active layer doping concentration, exhibit significant improvements in the breakdown voltage and capacitance relative to flat n‐active layer devices. It is found that the varactor diodes with a hyperabrupt doping profile are effective in shifting the breakdown voltage. Moreover, the capacitance in the hyperabrupt graded junction is comparatively more dependent on the reverse‐bias voltage than that in the uniformly doped junction. Experimental results indicate a maximum reverse breakdown voltage of 40 V at a leakage current of 165 µA. Furthermore, the maximum and minimum capacitances are 3.88 and 0.72 pF, respectively, for an anode diameter of 70 µm, resulting in a Cmax/Cmin ratio of 5.39. Packaged GaAs varactor diode for VCO applications.

A simple, practical way to evaluate process-induced oxygen precipitates was investigated. Effective values of fastest nucleation point (TC , J max) were derived as parameters of precipitate densities from the as-grown oxygen precipitate nuclei distributions by fitting them into the cumulative function F(T) of the nucleation rate J = J(Oi, CV, T). Precipitate densities were clearly explained by TC and J max in the entire Oi and point defect region. From the relations of Oi and Cv on the fastest nucleation point in the nucleation rate, TC is closely related to the CV and expected as a potential indicator of evaluating the practical CZ-Si manufacturing.