Electrical transport and current properties of rare-earth dysprosium Schottky electrode on p-type GaN at various annealing temperatures

The electrical and current transport properties of rapidly annealed Dy/p-GaN SBD are probed by I-V and C-V techniques. The estimated barrier heights（BH） of as-deposited and 200 ℃ annealed SBDs are 0.80 eV（I-V）/0.93 eV（C-V） and 0.87 eV（I-V）/1.03 eV（C-V）. However, the BH rises to 0.99 eV（I-V）/1.18 eV（C-V）and then slightly deceases to 0.92 eV（I-V）/1.03 eV（C-V） after annealing at 300 ℃ and 400 ℃. The utmost BH is attained after annealing at 300 ℃ and thus the optimum annealing for SBD is 300 ℃. By applying Cheung＇s functions, the series resistance of the SBD is estimated. The BHs estimated by I-V, Cheung＇s and ΨS-V plot are closely matched; hence the techniques used here are consistency and validity. The interface state density of the as-deposited and annealed contacts are calculated and we found that the NSS decreases up to 300 ℃ annealing and then slightly increases after annealing at 400 ℃. Analysis indicates that ohmic and space charge limited conduction mechanisms are found at low and higher voltages in forward-bias irrespective of annealing temperatures. Our experimental results demonstrate that the Poole-Frenkel emission is leading under the reverse bias of Dy/p-GaN SBD at all annealing temperatures.

Optical and Microstructural Characterisations of Pulsed rf Magnetron Sputtered Alumina Thin Film

Alumina thin films were deposited on fused quartz and SS304 substrate by pulsed rf magnetron sputtering with both direct and reactive methods. The films were characterised by energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy and atomic force microscopy to reveal the microstructure, surface morphology and topography of thin films. Transmittance and reflectance of alumina thin film were evaluated after deposition on the quartz substrate. Transmittance of the quartz remains almost un-altered when alumina was deposited by the reactive sputtering. A marginal decrease of ~4% in the transmittance of quartz was, however, observed after deposition of alumina by direct sputtering. Infrared emittance of the substrate also remains almost constant after deposition of thin alumina film. Further, as-deposited alumina on SS304 obtained by both direct and reactive sputtering process was amorphous in nature. However, after annealing crystalline peaks were observed.

Schottky barrier parameters and structural properties of rapidly annealed Zr Schottky electrode on p-type GaN

The Schottky barrier junction parameters and structural properties of Zr/p-GaN Schottky diode are explored at various annealing temperatures.Experimental analysis showed that the barrier height（BH）of the Zr/pGa N Schottky diode increases with annealing at 400°C（0.92 eV（I–V）/1.09 e V（C–V））compared to the asdeposited one（0.83 eV（I–V）/0.93 eV（C–V））.However,the BH decreases after annealing at 500°C.Also,at different annealing temperatures,the series resistance and BH are assessed by Cheung’s functions and their values compared.Further,the interface state density（NSS/of the diode decreases after annealing at 400°C and then somewhat rises upon annealing at 500°C.Analysis reveals that the maximum BH is obtained at 400°C,and thus the optimum annealing temperature is 400°C for the diode.The XPS and XRD analysis revealed that the increase in BH may be attributed to the creation of Zr–N phases with increasing annealing up to 400°C.The BH reduces for the diode annealed at 500°C,which may be due to the formation of Ga–Zr phases at the junction.The AFM measurements reveal that the overall surface roughness of the Zr film is quite smooth during rapid annealing process.