The electrical device characteristics of Ni/β-Ga2O3 vertical Schottky barrier diodes (SBDs) were measured in situ during the irradiation of 120 MeV Ag7+ swift heavy ions (SHIs). These devices exhibit SHI irradiation-induced degradation with 120 MeV Ag7+ ions in the ion fluence ranges of 1 × 1010 to 1 × 1012 ions/cm2. The height of the Schottky barrier is found to decrease from 1.11 to 0.93 eV, and the ideality factor increases from 1.16 to 2.06. These changes indicate the degradation of the device with SHI irradiation. A significant four orders increase is observed in the leakage current density from 4.04 × 10−8 to 1.98 × 10−4 A/cm2 at −1 V, and the series resistance also increases from 3.38 × 103 to 1.15 × 104 Ω. X-ray photoelectron spectroscopy measurements show that the Ga ions are present in divalent and trivalent states with the spectral features having the binding energies centered at 20.2 eV and 19.9 eV (Ga 3d core-levels) before and after ion irradiation. The O 2s peak shifts to 23.7 eV, and there is an increase in intensity and peak broadening due to the change in the trivalent to divalent state of Ga due to the irradiation. The O(I) peak appears at 530.7 eV in the pristine sample with the Ga–O bonding with the Ga3+ state in pure Ga2O3. Moreover, there is a significant change in the intensity and the peak width of O(II) centered at 533.0 eV after ion irradiation at the fluence of 1 × 1012 ions/cm2. This indicates that there is an increase in the surface adsorbed/lattice oxygen, resulting in GaO.
─ This research paper proposes a recently developed new variant of Particle Swarm Optimization (PSO) called Accelerated Particle Swarm Optimization (APSO) in speech enhancement application. Accelerated Particle Swarm Optimization technique is developed by Xin she Yang in 2010. APSO is simpler to implement and it has faster convergence when compared to the standard PSO (SPSO) algorithm. Hence as an alternative to SPSO based speech enhancement algorithm, APSO is introduced to speech enhancement in the present paper. The present study aims to analyze the performance of APSO and to compare it with existing standard PSO algorithm, in the context of dual channel speech enhancement. Objective evaluation of the proposed method is carried out by using three objective measures of speech quality SNR, Improved SNR, PESQ and one objective measure of speech intelligibility FAI. The performance of the algorithm is studied under babble and factory noise environments. Simulation result proves that APSO based speech enhancement algorithm is superior to the standard PSO based algorithm with an improved speech quality and intelligibility measures.
β-Ga 2 O 3 is an interesting new generation wide bandgap semiconductor for power device applications. The gamma irradiation was performed on the HfO 2 /β-Ga 2 O 3 -based metal-oxidesemiconductor capacitors at 1 kGy and 200 kGy doses. The leakage current density variation at −1 V is 3.47×10 −7 A cm −2 , 5.90×10 −7 A cm −2 and 4.91×10 −6 A cm −2 for the pristine, 1 kGy and 200 kGy devices, respectively. In the case of substrate injection, the Schottky emission mechanism appears to be dominant in the 0.65 to 2.0 MV cm −1 electric field range. The barrier heights (Ni/HfO 2 /β-Ga 2 O 3 ) 0.95 eV, 0.86 eV and 0.83 eV were extracted from Schottky emission for the pristine, 1 kGy and 200 kGy doses, respectively. However, as the dose increases to 200 kGy, the charge-trapping favors the trap-assisted Poole-Frenkel (PF) tunneling mechanism. In this case, the PF emission mechanism seems to be dominant for the pristine and 1 kGy in the range of 2.0-4.0 MV cm −1 , whereas for 200 kGy it is 1.45 to 4.0 MV cm −1 which indicates that the defect assisted PF tunneling is predominant at 200 kGy irradiation dose. There is an increase in the density of oxide traps (D ot ) changes from 1.14×10 12 cm −2 eV −1 to 1.47×10 12 cm −2 eV −1 , and the density of interface traps has increased from 1.95× 10 11 cm −2 eV −1 to 3.80×10 11 cm −2 eV −1 for the pristine and 200 kGy samples, respectively. The peaks of Photoluminescence show that the three bands of defects centered at 3.0, 2.7 and 2.2 eV. These peaks have possibly arisen from the vacancies of oxygen. At 200 kGy high dose, the defect band emissions were found at 2.9, 2.6 eV and a broad emission at 2.1 eV indicates the increase in the denisty of oxide-trapped charges within the HfO 2 layer.
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