Compositionally undulating step-graded Al（Ga）InxAs （x = 0.05-0.52） buffers with the following InP layer were grown by metal-organic chemical vapor deposition （MOCVD） on （001） GaAs with a 15° miscut. The d...Compositionally undulating step-graded Al（Ga）InxAs （x = 0.05-0.52） buffers with the following InP layer were grown by metal-organic chemical vapor deposition （MOCVD） on （001） GaAs with a 15° miscut. The dislocation dis- tribution and tilts of the epilayers were examined using x-ray rocking curve and （004） reciprocal space maps （RSM） along two orthogonal （110） directions. The results suggested that such reverse-graded layers have different effects on a and 13 dislocations. A higher dislocation density was observed along the [ 110] direction and an epilayer tilt of - 1.43° was attained in the [1-10] direction when a reverse-graded layer strategy was employed. However, for conventional step-graded samples, the dislocation density is normally higher along the [1-10] direction.展开更多
The electron mobility anisotropy in (Al,Ga)Sb/InAs two-dimensional electron gases with different surface morphology has been investigated.Large electron mobility anisotropy is found for the sample with anisotropic mor...The electron mobility anisotropy in (Al,Ga)Sb/InAs two-dimensional electron gases with different surface morphology has been investigated.Large electron mobility anisotropy is found for the sample with anisotropic morphology,which is mainly induced by the threading dislocations in the InAs layer.For the samples with isotropic morphology,the electron mobility is also anisotropic and could be attributed to the piezoelectric scattering.At low temperature (below transition temperature),the piezoelectric scattering is enhanced with the increase of temperature,leading to the increase of electron mobility anisotropy.At high temperature (above transition temperature),the phonon scattering becomes dominant.Because the phonon scattering is isotropic,the electron mobility anisotropy in all the samples would be reduced.Our results provide useful information for the comprehensive understanding of electron mobility anisotropy in the (Al,Ga)Sb/InAs system.展开更多
One-band effective mass model is used to simulation of electron gas properties in quantum well. We calculate of dispersion curves for first three subbands. Calculation results of Fermi energy, effective mass at Fermi ...One-band effective mass model is used to simulation of electron gas properties in quantum well. We calculate of dispersion curves for first three subbands. Calculation results of Fermi energy, effective mass at Fermi level as function of electron concentration are presented. The obtained results are good agreement with the experimental dates.展开更多
The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of cat...The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of catalysts, particularly a high content of coordinatively unsaturated Al3+sites(penta-coordinated Al3+,denoted as Al3+penta) could lead to a remarkably improved dehydrogenation activity of the catalyst. The bulk characterization reveals that the sufficient amount of Al3+pentain Al2O3 benefit the dispersion of Pt and Ga2O3 on the Al2O3 support. At the same time, TPR results reveal that the presence of Pt facilitates the reduction of Ga2O3, likely due to the hydrogen spillover between the well dispersed Pt and Ga2O3,which consequently enhances the synergistic function between Pt and Ga2O3 in the dehydrogenation of propane. Recyclability tests demonstrate that the dehydrogenation activity stabilizes after three cycles over the Pt/Ga/Al2O3 catalyst.展开更多
In this report, the effect of temperature on the In As/Al Sb heterojunction and high-electron-mobility transistors（HEMTs） with a gate length of 2 μm are discussed comprehensively. The results indicate that device p...In this report, the effect of temperature on the In As/Al Sb heterojunction and high-electron-mobility transistors（HEMTs） with a gate length of 2 μm are discussed comprehensively. The results indicate that device performance is greatly improved at cryogenic temperatures. It is also observed that the device performance at 90 K is significantly improved with 27% lower gate leakage current, 12% higher maximum drain current, and 22.5% higher peak transconductance compared to 300 K. The temperature dependence of mobility and the two-dimensional electron gas concentration in the In As/Al Sb heterojunction for the temperature range 90 K-300 K is also investigated. The electron mobility at 90 K（42560 cm2/V·s）is 2.5 times higher than its value at 300 K（16911 cm^2/V·s） because of the weaker lattice vibration and the impurity ionization at cryogenic temperatures, which corresponds to a reduced scattering rate and higher mobility. We also noted that the two-dimensional electron gas concentration decreases slightly from 1.99 × 10^（12） cm^（-2） at 300 K to 1.7 × 10^（12） cm^（-2） at 90 K with a decrease in temperature due to the lower ionization at cryogenic temperature and the nearly constant ？Ec.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61376065)
文摘Compositionally undulating step-graded Al（Ga）InxAs （x = 0.05-0.52） buffers with the following InP layer were grown by metal-organic chemical vapor deposition （MOCVD） on （001） GaAs with a 15° miscut. The dislocation dis- tribution and tilts of the epilayers were examined using x-ray rocking curve and （004） reciprocal space maps （RSM） along two orthogonal （110） directions. The results suggested that such reverse-graded layers have different effects on a and 13 dislocations. A higher dislocation density was observed along the [ 110] direction and an epilayer tilt of - 1.43° was attained in the [1-10] direction when a reverse-graded layer strategy was employed. However, for conventional step-graded samples, the dislocation density is normally higher along the [1-10] direction.
基金supported by NSFC (Grants No. 11834013 and 12174383)support from the Youth Innovation Promotion Association, Chinese Academy of Sciences (No. 2021110)。
文摘The electron mobility anisotropy in (Al,Ga)Sb/InAs two-dimensional electron gases with different surface morphology has been investigated.Large electron mobility anisotropy is found for the sample with anisotropic morphology,which is mainly induced by the threading dislocations in the InAs layer.For the samples with isotropic morphology,the electron mobility is also anisotropic and could be attributed to the piezoelectric scattering.At low temperature (below transition temperature),the piezoelectric scattering is enhanced with the increase of temperature,leading to the increase of electron mobility anisotropy.At high temperature (above transition temperature),the phonon scattering becomes dominant.Because the phonon scattering is isotropic,the electron mobility anisotropy in all the samples would be reduced.Our results provide useful information for the comprehensive understanding of electron mobility anisotropy in the (Al,Ga)Sb/InAs system.
文摘One-band effective mass model is used to simulation of electron gas properties in quantum well. We calculate of dispersion curves for first three subbands. Calculation results of Fermi energy, effective mass at Fermi level as function of electron concentration are presented. The obtained results are good agreement with the experimental dates.
基金Supported by the National Natural Science Foundation of China(61534006,61974152,61505237,61505235,61404148,61176082)the National Key Research and Development Program of China(2016YFB0402403)the Youth Innovation Promotion Association,CAS(2016219)
基金the National Natural Science Foundation of China(No.21676195)the China Postdoctoral Science Foundation(2016M601347)。
文摘The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+determines the bulk structure of catalysts, particularly a high content of coordinatively unsaturated Al3+sites(penta-coordinated Al3+,denoted as Al3+penta) could lead to a remarkably improved dehydrogenation activity of the catalyst. The bulk characterization reveals that the sufficient amount of Al3+pentain Al2O3 benefit the dispersion of Pt and Ga2O3 on the Al2O3 support. At the same time, TPR results reveal that the presence of Pt facilitates the reduction of Ga2O3, likely due to the hydrogen spillover between the well dispersed Pt and Ga2O3,which consequently enhances the synergistic function between Pt and Ga2O3 in the dehydrogenation of propane. Recyclability tests demonstrate that the dehydrogenation activity stabilizes after three cycles over the Pt/Ga/Al2O3 catalyst.
基金supported by the National Natural Science Foundation of China (No. 51505323)the Applied Basic Research Program of Shanxi Province,China (Nos. 20210302123117, 20210302124658)。
基金Project supported by the Advanced Research Foundation of China(Grant No.914xxx803-051xxx111)the National Defense Advanced Research Project of China(Grant No.315xxxxx301)the National Defense Innovation Program of China(Grant No.48xx4)
文摘In this report, the effect of temperature on the In As/Al Sb heterojunction and high-electron-mobility transistors（HEMTs） with a gate length of 2 μm are discussed comprehensively. The results indicate that device performance is greatly improved at cryogenic temperatures. It is also observed that the device performance at 90 K is significantly improved with 27% lower gate leakage current, 12% higher maximum drain current, and 22.5% higher peak transconductance compared to 300 K. The temperature dependence of mobility and the two-dimensional electron gas concentration in the In As/Al Sb heterojunction for the temperature range 90 K-300 K is also investigated. The electron mobility at 90 K（42560 cm2/V·s）is 2.5 times higher than its value at 300 K（16911 cm^2/V·s） because of the weaker lattice vibration and the impurity ionization at cryogenic temperatures, which corresponds to a reduced scattering rate and higher mobility. We also noted that the two-dimensional electron gas concentration decreases slightly from 1.99 × 10^（12） cm^（-2） at 300 K to 1.7 × 10^（12） cm^（-2） at 90 K with a decrease in temperature due to the lower ionization at cryogenic temperature and the nearly constant ？Ec.
