In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-depen...In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.展开更多
The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） an...The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） and current–voltage（I–V） characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field（PCF） scattering exhibits a significant impact on RSat the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.展开更多
AIN and Al2N2 have been observed in the record of time-of-flight mass-spectra as positive ions. Associating with density functional theory(DFT) B3LYP method with 6-31G* basis set, we have carried out the optimizing ca...AIN and Al2N2 have been observed in the record of time-of-flight mass-spectra as positive ions. Associating with density functional theory(DFT) B3LYP method with 6-31G* basis set, we have carried out the optimizing calculations of the geometry, electronic state and vibrational frequency for (AIN)n (n = 1-15) clusters, moreover, discussed the character of the chemical bond and thermodynamical stability and explained the experimental mass spectra. The results show that there do not exist AI-AI and N-N bonds and only exists AI-N bond in the ground state structures of (AIN)n clusters; and the "magical number" regularity of (AIN)n is those whose atom number Is 4, 8, 12,16, 20, etc, all of which are times of four.展开更多
Using density functional theory (DFT) method with 6-31G* basis set, we have carried out the optimizing calculation of geometry, vibrational frequency and thermodynamical stability for(AIN)n+ and (AIN)n- (n =1-15) clus...Using density functional theory (DFT) method with 6-31G* basis set, we have carried out the optimizing calculation of geometry, vibrational frequency and thermodynamical stability for(AIN)n+ and (AIN)n- (n =1-15) clusters. Moreover, their ionic potential (IP) and electron affinity(EA) were discussed. The results show that the electrical charge condition of the cluster has a relatively great impact on the structure of the cluster and with the increase of n, this kind of impactis reduced gradually. There are no AI-AI and N-N bonds in the stable structure of (AIN)n+ or (AIN)n-, and the AI-N bond is the sole bond type. The magic number regularity of (AIN)n+, and (AIN)n- is consistent with that for (AIN)n, indicating that the structure with even n such as 2, 4,6, … is more stable. In addition, (AIN)10 has the maximal ionization power (9.14 eV) and the minimal electron affinity energy (0.19 eV), which manifests that (AIN)10 is more stable than other clusters.展开更多
Subsolidus phase relationships in the system Ln2O3-Si3N4-AIN-AI2O3, where Ln represents Nd, Sm and Dy, were summarized, with emphasis on the region involving α-sialon, β-sialon and AIN-polytypoid phases. This inform...Subsolidus phase relationships in the system Ln2O3-Si3N4-AIN-AI2O3, where Ln represents Nd, Sm and Dy, were summarized, with emphasis on the region involving α-sialon, β-sialon and AIN-polytypoid phases. This information is further used in designing the compatible matrix phases of sialon materials with desirable properties. Examples were provided to illustrate the advantage of such a basic approach to materials design.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174182 and 61306113)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110131110005)
文摘In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174182,11574182,and 61306113)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110131110005)
文摘The parasitic source resistance（RS） of AlGaN/AlN/GaN heterostructure field-effect transistors（HFETs） is studied in the temperature range 300–500 K. By using the measured RSand both capacitance–voltage（C–V） and current–voltage（I–V） characteristics for the fabricated device at 300, 350, 400, 450, and 500 K, it is found that the polarization Coulomb field（PCF） scattering exhibits a significant impact on RSat the above-mentioned different temperatures. Furthermore, in the AlGaN/AlN/GaN HFETs, the interaction between the additional positive polarization charges underneath the gate contact and the additional negative polarization charges near the source Ohmic contact, which is related to the PCF scattering, is verified during the variable-temperature study of RS.
文摘AIN and Al2N2 have been observed in the record of time-of-flight mass-spectra as positive ions. Associating with density functional theory(DFT) B3LYP method with 6-31G* basis set, we have carried out the optimizing calculations of the geometry, electronic state and vibrational frequency for (AIN)n (n = 1-15) clusters, moreover, discussed the character of the chemical bond and thermodynamical stability and explained the experimental mass spectra. The results show that there do not exist AI-AI and N-N bonds and only exists AI-N bond in the ground state structures of (AIN)n clusters; and the "magical number" regularity of (AIN)n is those whose atom number Is 4, 8, 12,16, 20, etc, all of which are times of four.
基金This work was supported by the Backbone Teacher of Chinese University Sustentation Fund of the Ministry of Education of China and the Natural Science Foundation of Shanxi Province.
文摘Using density functional theory (DFT) method with 6-31G* basis set, we have carried out the optimizing calculation of geometry, vibrational frequency and thermodynamical stability for(AIN)n+ and (AIN)n- (n =1-15) clusters. Moreover, their ionic potential (IP) and electron affinity(EA) were discussed. The results show that the electrical charge condition of the cluster has a relatively great impact on the structure of the cluster and with the increase of n, this kind of impactis reduced gradually. There are no AI-AI and N-N bonds in the stable structure of (AIN)n+ or (AIN)n-, and the AI-N bond is the sole bond type. The magic number regularity of (AIN)n+, and (AIN)n- is consistent with that for (AIN)n, indicating that the structure with even n such as 2, 4,6, … is more stable. In addition, (AIN)10 has the maximal ionization power (9.14 eV) and the minimal electron affinity energy (0.19 eV), which manifests that (AIN)10 is more stable than other clusters.
文摘Subsolidus phase relationships in the system Ln2O3-Si3N4-AIN-AI2O3, where Ln represents Nd, Sm and Dy, were summarized, with emphasis on the region involving α-sialon, β-sialon and AIN-polytypoid phases. This information is further used in designing the compatible matrix phases of sialon materials with desirable properties. Examples were provided to illustrate the advantage of such a basic approach to materials design.
