基于0.25μm Ga N HEMT工艺,研制了一款S波段Ga N功率放大器单片微波集成电路（MMIC）。该电路采用三级拓扑放大结构,提高了放大器的增益;采用电抗匹配方式,减小了电路输出级的损耗,提高了MMIC的功率和效率。输出级有源器件的布局优化,...基于0.25μm Ga N HEMT工艺,研制了一款S波段Ga N功率放大器单片微波集成电路（MMIC）。该电路采用三级拓扑放大结构,提高了放大器的增益;采用电抗匹配方式,减小了电路输出级的损耗,提高了MMIC的功率和效率。输出级有源器件的布局优化,改善了放大器芯片的温度分布特性。测试结果表明,在2.8~3.6 GHz测试频带内,在脉冲偏压28 V（脉宽100μs,占空比10%）时,峰值输出功率大于60W,功率附加效率大于45%,小信号增益大于34 d B,增益平坦度在±0.3 d B以内,输入电压驻波比在1.7以下;在稳态偏压28 V时,连续波饱和输出功率大于40 W,功率附加效率38%以上。该MMIC尺寸为4.2 mm×4.0 mm。展开更多
Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with t...Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with the addition of Ga2S3, two main structural transformations were deduced ： the gradual enhancement of ethane- like structural units S3 Ge- GeS3 （ 250 cm ^- 1） and S3 Ga- GaS3 （270 cm ^- 1 ） and the appearance of charge imbalanced units [ Ga2 S2 （ S1/2 ）4 ]^2- and [Ga（ S1/2 ）4 ]^- . And this change of structural aspect seems to give as a clue to understanding the cause of the increased rare-earth solubility.展开更多
High-performance Al Ga N/Ga N high electron mobility transistors（HEMTs） grown on silicon substrates by metal–organic chemical-vapor deposition（MOCVD） with a selective non-planar n-type Ga N source/drain（S/D） re...High-performance Al Ga N/Ga N high electron mobility transistors（HEMTs） grown on silicon substrates by metal–organic chemical-vapor deposition（MOCVD） with a selective non-planar n-type Ga N source/drain（S/D） regrowth are reported. A device exhibited a non-alloyed Ohmic contact resistance of 0.209 Ω·mm and a comprehensive transconductance（gm） of 247 m S/mm. The current gain cutoff frequency f T and maximum oscillation frequency f MAX of 100-nm HEMT with S/D regrowth were measured to be 65 GHz and 69 GHz. Compared with those of the standard Ga N HEMT on silicon substrate, the fTand fMAXis 50% and 52% higher, respectively.展开更多
The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the...The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.展开更多
文摘基于0.25μm Ga N HEMT工艺,研制了一款S波段Ga N功率放大器单片微波集成电路（MMIC）。该电路采用三级拓扑放大结构,提高了放大器的增益;采用电抗匹配方式,减小了电路输出级的损耗,提高了MMIC的功率和效率。输出级有源器件的布局优化,改善了放大器芯片的温度分布特性。测试结果表明,在2.8~3.6 GHz测试频带内,在脉冲偏压28 V（脉宽100μs,占空比10%）时,峰值输出功率大于60W,功率附加效率大于45%,小信号增益大于34 d B,增益平坦度在±0.3 d B以内,输入电压驻波比在1.7以下;在稳态偏压28 V时,连续波饱和输出功率大于40 W,功率附加效率38%以上。该MMIC尺寸为4.2 mm×4.0 mm。
文摘Roman scattering measurement of （ 1 - x ） GeS2-x Ga2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3 . According to the change of Raman spectra with the addition of Ga2S3, two main structural transformations were deduced ： the gradual enhancement of ethane- like structural units S3 Ge- GeS3 （ 250 cm ^- 1） and S3 Ga- GaS3 （270 cm ^- 1 ） and the appearance of charge imbalanced units [ Ga2 S2 （ S1/2 ）4 ]^2- and [Ga（ S1/2 ）4 ]^- . And this change of structural aspect seems to give as a clue to understanding the cause of the increased rare-earth solubility.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61401373)the Fundamental Research Funds for Central Universities,China(Grant No.XDJK2013B004)the Research Fund for the Doctoral Program of Southwest University,China(Grant No.SWU111030)
文摘High-performance Al Ga N/Ga N high electron mobility transistors（HEMTs） grown on silicon substrates by metal–organic chemical-vapor deposition（MOCVD） with a selective non-planar n-type Ga N source/drain（S/D） regrowth are reported. A device exhibited a non-alloyed Ohmic contact resistance of 0.209 Ω·mm and a comprehensive transconductance（gm） of 247 m S/mm. The current gain cutoff frequency f T and maximum oscillation frequency f MAX of 100-nm HEMT with S/D regrowth were measured to be 65 GHz and 69 GHz. Compared with those of the standard Ga N HEMT on silicon substrate, the fTand fMAXis 50% and 52% higher, respectively.
基金supported by the National Natural Science Foundation of China(NSFC)under grant nos.61574059 and 61722402the National Key Research and Development Program of China(2016YFB0700700)+1 种基金Shu-Guang program(15SG20)CC of ECNU
文摘The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.
