| With the increasing application of wide bandgap semiconductor materials in electronics,energy,military and other fields,the demand for more high-temperature and high-pressure power devices is also increasing.It is foreseeable that high-voltage,low-loss,high-performance power devices will become a battleground in the semiconductor field in the future.Compared with the widely used SiC and GaN,β-Ga2O3 has a wider band gap,higher breakdown field strength and Baliga’s figure of merit,and lower preparation cost and higher efficiency.With these advantages,β-Ga2O3 has attracted the attention of researchers in the semiconductor industry,and related research is also underway.The main research results are as follows:1.Study on the properties of(011)planeA kind of dislocation occurring on the surface of β-Ga2O3(001)substrate and line-shaped defects caused by these dislocations in the epitaxial layer are responsible for reverse leakage current and breakdown of power devices.Therefore,this type of dislocation is very disadvantageous for the performance of power devices,and β-Ga2O3(011)plane can effectively reduce or even completely avoid the influence of this defect due to its parallel relationship with this kind of dislocation.However,there is still a lack of systematic evaluation of the performance of this crystal plane.In order to determine whether the(011)plane is a potential substrate orientation,a series of(011)-oriented substrates were processed from β-Ga2O3 bulk crystal grown by edge-defined film-fed growth(EFG)method to take some research.The high quality of the substrate was proved for the full width at half maximum(FWHM)was 66.79 arcsec in X-ray rocking curve and the wet etching method was used to study the dislocation distribution.The low-dislocation-density characteristic of the(011)plane was confirmed and the quadrilateral etch pit was observed by atomic force microscopy(AFM)which indicated these etch pits were caused by other defects.In addition,the photoelectric properties and the element composition of the(011)plane were evaluated through Raman spectra,optical transmittance spectra and X-ray photoelectron spectroscopy(XPS).The results indicated that the(011)plane not only has the low-dislocation-density characteristic,but also has excellent photoelectric properties.At the same time,benefiting from the absence of this kind of dislocation mentioned above,β-Ga2O3(011)plane could be a potential substrate orientation for high quality epitaxial layer.2.The scheme optimization of β-Ga2O3 crystal grown by edge-defined film-fed growth methodThere are two dissociation planes in β-Ga2O3 crystal,(100)and(001)planes,and the angle between them is 103.8°.At present,the main growth plane of the EFG method is also these two crystal planes,and the(001)plane is more used as the growth plane.Therefore,in the process of growth,the crystal often cracks from the surface along the direction of the dissociation surface due to the presence of thermal stress.In addition,when studying the defect distribution of the substrate,the defect density near the surface is much higher than that in the center.In order to explain the causes of these phenomena,reduce the occurrence of cracks and improve the quality of the crystal,in this paper,we used CGSim software to model along the thickness direction of the guided mode method.It is calculated that the thermal stress in the growth process is mainly concentrated on the outside of the crystal and the shoulder.The reason for the crack during the growth of the crystal,especially when the thickness is enlarged,and the effects of growth schemes or processes such as insulator and shoulder angle on the thermal stress inside the crystal were explored.The significance of various changes to crystal growth was pointed out,and guiding suggestions were put forward for practical experiments. |
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