A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is ...A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is larger than 120. By use of device simulation,the cause of NDR is that increasing collector voltage makes the ultrathin base reach through and the device transforms from a bipolar state to a bulk barrier state. In addition, the simulated cutoff frequency is about 60-80GHz.展开更多
We report the performance of the first self-aligned InP/InGaAs double heterojunction bipolar transistor （DHBT） produced in China. The device has a 2μm × 12μm U-shaped emitter area and demonstrates a peak comm...We report the performance of the first self-aligned InP/InGaAs double heterojunction bipolar transistor （DHBT） produced in China. The device has a 2μm × 12μm U-shaped emitter area and demonstrates a peak common-emitter DC current gain of over 300,an offset voltage of 0. 16V,a knee voltage of 0.6V,and an open-base breakdown voltage of about 6V. The HBT exhibits good microwave performance with a current gain cutoff fre- quency of 80GHz and a maximum oscillation frequency of 40GHz. These results indicate that this InP/InGaAs DHBT is suitable for low-voltage, low-power, and high-frequency applications.展开更多
The effects of solvent and impurity on the crystal habit of 11α-hydroxy-16α,17α-epoxyprogesterone (HEP)grown from solution were studied by scanning electron microscope.Long prismatic crystals were produced when HEP...The effects of solvent and impurity on the crystal habit of 11α-hydroxy-16α,17α-epoxyprogesterone (HEP)grown from solution were studied by scanning electron microscope.Long prismatic crystals were produced when HEP was crystallized from pure acetone and N,N-dimethylformamide,while blocky crystals were produced from pure chloroform by cooling crystallization.One kind of isomorphic impurity,16α,17α-epoxyprogesterone(EP) was selected to examine its effect on the HEP crystal habit.When the content of EP in the mother liquor is very high(55.45%,solvent free basis),the habit of produced HEP crystals was greatly modified from prismatic to octa-hedral.The differential scanning calorimetry and X-ray powder diffraction analyses showed that the change of crystal habit was originated from the crystal structure modification.展开更多
The mineralogy of shock vein matrix in the Suizhou meteorite has been investigated by optical and transmission electron microscopy. It was revealed that the vein matrix is composed of majorite-pyrope garnet, mag- aesi...The mineralogy of shock vein matrix in the Suizhou meteorite has been investigated by optical and transmission electron microscopy. It was revealed that the vein matrix is composed of majorite-pyrope garnet, mag- aesiowtistite, and ringwoodite, with FeNi-FeS inter- growths. The observation and character of ring-like selected electron diffraction （SAED） patterns indicate that Lhe idiomorphic garnet crystals in the vein matrix have different orientations. The polycrystalline nature of magnesiowtistite is also confirmed by a ring-like SAED pattern. Both garnet and magnesiowtistite crystals showed sharp Jiffraction spots, signifying the good crystallinity of these ：wo minerals. The SAED pattern of cryptocrystalline 5ngwoodite shows only diffuse concentric diffraction tings. FeNi metal and troilite （FeS）, which were molten during the shock event, occur in the matrix as fine eutectic FeNi-FeS intergrowths filling the interstices between garaet and magnesiowiistite grains. Based on the phase dia- gram of the Allende chondrite and the results of this TEM study, it is inferred that majorite-pyrope garnet first crystallized from the Suizhou chondritic melt at 22-26 GPa, Followed by crystallization of magnesiowtistite at 20-24 GPa, and then ringwoodite at 18-20 GPa. The eutectic intergrowths of FeNi-metal and troilite are proposed to have crystallized during meteorite cooling and solidified at the last stage of vein formation.展开更多
文摘A novel mesa ultra-thin base AlGaAs/GaAs HBT is designed and fabricated with wet chemical selective etch technique and monitor electrode technique. It has a particular and obvious voltage-controlled NDR whose PVCR is larger than 120. By use of device simulation,the cause of NDR is that increasing collector voltage makes the ultrathin base reach through and the device transforms from a bipolar state to a bulk barrier state. In addition, the simulated cutoff frequency is about 60-80GHz.
文摘We report the performance of the first self-aligned InP/InGaAs double heterojunction bipolar transistor （DHBT） produced in China. The device has a 2μm × 12μm U-shaped emitter area and demonstrates a peak common-emitter DC current gain of over 300,an offset voltage of 0. 16V,a knee voltage of 0.6V,and an open-base breakdown voltage of about 6V. The HBT exhibits good microwave performance with a current gain cutoff fre- quency of 80GHz and a maximum oscillation frequency of 40GHz. These results indicate that this InP/InGaAs DHBT is suitable for low-voltage, low-power, and high-frequency applications.
文摘The effects of solvent and impurity on the crystal habit of 11α-hydroxy-16α,17α-epoxyprogesterone (HEP)grown from solution were studied by scanning electron microscope.Long prismatic crystals were produced when HEP was crystallized from pure acetone and N,N-dimethylformamide,while blocky crystals were produced from pure chloroform by cooling crystallization.One kind of isomorphic impurity,16α,17α-epoxyprogesterone(EP) was selected to examine its effect on the HEP crystal habit.When the content of EP in the mother liquor is very high(55.45%,solvent free basis),the habit of produced HEP crystals was greatly modified from prismatic to octa-hedral.The differential scanning calorimetry and X-ray powder diffraction analyses showed that the change of crystal habit was originated from the crystal structure modification.
基金financially supported by National Natural Science foundation of China under Grant 41172046 and 40972044 in part
文摘The mineralogy of shock vein matrix in the Suizhou meteorite has been investigated by optical and transmission electron microscopy. It was revealed that the vein matrix is composed of majorite-pyrope garnet, mag- aesiowtistite, and ringwoodite, with FeNi-FeS inter- growths. The observation and character of ring-like selected electron diffraction （SAED） patterns indicate that Lhe idiomorphic garnet crystals in the vein matrix have different orientations. The polycrystalline nature of magnesiowtistite is also confirmed by a ring-like SAED pattern. Both garnet and magnesiowtistite crystals showed sharp Jiffraction spots, signifying the good crystallinity of these ：wo minerals. The SAED pattern of cryptocrystalline 5ngwoodite shows only diffuse concentric diffraction tings. FeNi metal and troilite （FeS）, which were molten during the shock event, occur in the matrix as fine eutectic FeNi-FeS intergrowths filling the interstices between garaet and magnesiowiistite grains. Based on the phase dia- gram of the Allende chondrite and the results of this TEM study, it is inferred that majorite-pyrope garnet first crystallized from the Suizhou chondritic melt at 22-26 GPa, Followed by crystallization of magnesiowtistite at 20-24 GPa, and then ringwoodite at 18-20 GPa. The eutectic intergrowths of FeNi-metal and troilite are proposed to have crystallized during meteorite cooling and solidified at the last stage of vein formation.
