High-purity InP layers have been successfully grown by metalorganic chemical vapor deposition (MOCVD) using tertiarybutylphosphine (TBP) as a phosphorus source. The highest quality InP layer, which was grown at a V/III ratio of 36, a growth temperature of 600 °C and a growth pressure of 760 Torr, exhibited electron mobility as high as 167 000 cm2/V s and carrier concentrations as low as 1.8×1014 cm−3 at 77 K. The film quality strongly depended on the silicon content as an impurity in TBP. Electron mobility at 77 K was dependent on the silicon content, changing its value from 10 100 cm2/V s (Si content; 0.8 ppm) to 167 000 cm2/V s (Si content; <0.03 ppm). The low-temperature (4.2 K) optical properties were also affected by silicon content as a impurity. It was found that electron mobility of 167 000 cm2/V s was the highest ever reported for InP grown by MOCVD using TBP as a phosphorus source. The quality of InP grown using TBP was equivalent to that of InP grown using phosphine (PH3).
Net hydrogen off-gas from the continuous catalyst regeneration type catalytic reforming process (CCR process) contains inorganic chlorides. In order to prevent potential problems such as corrosion in the downstream processes, such chlorides are commonly removed by using fixed-bed chloride traps. We have extensively investigated the chloride removal properties of various materials for the chloride traps and have developed effective and practical zinc oxide based chloride traps. Firstly, we found that net hydrogen off-gas from the CCR process contains not only inorganic chlorides but also organic chlorides. Secondly, we found that the widely used activated alumina based chloride traps have the major disadvantages of formation of organic chlorides from inorganic chlorides on the surface and leakage of the organic chlorides to the downstream processes. These organic chlorides may be decomposed by heating and may cause corrosion in the downstream processes. Conversely, we found that zinc oxide based chloride traps have high potential to remove both inorganic chlorides and organic chlorides through the presumptive mechanism that organic chlorides are converted into inorganic chlorides on the surface and are then trapped by reaction with zinc oxide. However, zinc oxide based chloride traps have problems with pellet breakage and pressure drop buildup due to the deliquescence of zinc chloride derived from the reactions of chloride compounds and zinc oxide. To solve these problems, the chemical and physical properties have been improved by appropriate reduction of zinc oxide content and increase of pore volume with addition of porous inorganic materials to increase the contribution of zinc oxide inside pellets to chlorine removal and to enhance zinc chloride retention capacity. Consequently, we developed a new zinc oxide chloride based chloride trap, JCL-1. Demonstration tests of the JCL-1 showed stable operation with effective removal of both inorganic chlorides and organic chlorides without pressure drop buildup or pellet breakage.
First successful fabrication of HBTs which can reduce the extrinsic base-collector capacitance C,, by selective multisteps MOCVD regrowth techniques is demonstrated. We have achieved cutoff frequency f of the regrown-HBTs with a large 6x 18 pm'emitter'areaof 59.6 GHz, which is superior to that of conventional HBTs of 40.2 GHz. The differences of total delay time of the regrown-HBT and conventional HBT was in good agreement with the collector charging time difference estimated from the device geometry, which indicates improvement of the high speed performance were achieved by the reduction of the C,,.
MOCVD-grown carbon(C>doped InGaAs layers using CBr4 as a C source were investigated with the Van der Pauw method and PL measurement. A hole concentration of as high as 7 X IOI9 was obtained at a growth temperature of 385 "c. However, PL intensity of the C-InGaAs &pen& on the growth temperature, and was weaker than that of Mg-or Zn-doped InGaAs at a range of over I X IOi9Furthermore. IDC measurement of DHBTs revealed that there existed a strict t r a b f f between the current gain and base sheet resistance of C-InGaAs unifombase D-HBTs. To break through the tradeoff, we have fabricated D-HBTs with 150-nm-thick strain-compensated gra&d-In,-XGaxAs-base (X=0.4230.53). As a result, a current gain of 55 with a base shect resistance of 480 Q/o were achieved.
The title reaction shown gives an activation volume of +38 ± 1 cm3mol‐1, which is among the largest positive activation volumes ever observed for electron‐transfer reactions of metal complexes.
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