Recent progresses in thermal treatment of β-Ga_(2)O_(3) single crystals and devices

In recent years,ultra-wide bandgap β-Ga_(2)O_(3) has emerged as a fascinating semiconductor material due to its great potential in power and photoelectric devices.In semiconductor industrial,thermal treatment has been widely utilized as a convenient and effective approach for substrate property modulation and device fabrication.Thus,a thorough summary of β-Ga_(2)O_(3) substrates and devices behaviors after high-temperature treatment should be significant.In this review,we present the recent advances in modulating properties of β-Ga_(2)O_(3) substrates by thermal treatment,which include three major applications:(ⅰ)tuning surface electrical properties,(ⅱ)modifying surface morphology,and(ⅲ)oxidating films.Meanwhile,regulating electrical contacts and handling with radiation damage and ion implantation have also been discussed in device fabrication.In each category,universal annealing conditions were speculated to figure out the corresponding problems,and some unsolved questions were proposed clearly.This review could construct a systematic thermal treatment strategy for various purposes and applications of β-Ga_(2)O_(3).

Defects evolution in n-type 4H-SiC induced by electron irradiation and annealing

Radiation damage produced in 4H-SiC by electrons of different doses is presented by using multiple characterization techniques. Raman spectra results indicate that SiC crystal structures are essentially impervious to 10 Me V electron irradiation with doses up to 3000 kGy. However, irradiation indeed leads to the generation of various defects, which are evaluated through photoluminescence(PL) and deep level transient spectroscopy(DLTS). The PL spectra feature a prominent broad band centered at 500 nm, accompanied by several smaller peaks ranging from 660 to 808 nm. The intensity of each PL peak demonstrates a linear correlation with the irradiation dose, indicating a proportional increase in defect concentration during irradiation. The DLTS spectra reveal several thermally unstable and stable defects that exhibit similarities at low irradiation doses.Notably, after irradiating at the higher dose of 1000 kGy, a new stable defect labeled as R_(2)(Ec-0.51 eV) appeared after annealing at 800 K. Furthermore, the impact of irradiation-induced defects on SiC junction barrier Schottky diodes is discussed. It is observed that high-dose electron irradiation converts SiC n-epilayers to semi-insulating layers. However, subjecting the samples to a temperature of only 800 K results in a significant reduction in resistance due to the annealing out of unstable defects.

Characterization of dissolved organic matter in urban sewage using excitation emission matrix fluorescence spectroscopy and parallel factor analysis

Wastewater dissolved organic matter （DOM） from different processing stages of a sewage treatment plant in Xiamen was characterized using fluorescence and absorption spectroscopy. Parallel factor analysis modeling of excitation-emission matrix spectra revealed five fluorescent components occurring in sewage DOM： one protein-like （C1）, three humic-like （C2, C4 and C5） and one xenobiotic-like （C3） components. During the aerated grit chamber and primary sedimentation tank stage, there was only a slight decrease in fluorescence intensity and the absorption coefficient at 350 nm （a 350 ）. During the second aeration stage, high concentration of protein-like and short-wavelength-excited humic-like components were significantly degraded accompanied by significant loss of DOC （80%） and a 350 （30%）, indicating that C1 and C2 were the dominant constituents of sewage DOM. As a result, long-wavelength- excited C4 and C5 became the dominant humic-like components and the DOM molecular size inferred from the variation of spectral slope S （300–650 nm） and specific absorption （a 280 /DOC） increased. Combination use of F max of C1 and the ratio of C1/C5, or a 350 may provide a quantitative indication for the relative amount of raw or treated sewage in aquatic environment.