Browsing by Author "CHANG, SJ"

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BLOCK COPOLYETHERESTERS .3. PREPARATION OF BLOCK COPOLYETHERESTERS BY A TEREPHTHALIC ACID PROCESS IN THE PRESENCE OF SALTS
(1995-01-01)
CHANG, SJ
;
CHANG, FC
;
TSAI, HB
;
應用化學系
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Department of Applied Chemistry
The block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolyetheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
LIGHT-INDUCED SIDEGATING EFFECT IN GAAS-MESFETS
(1993-12-01)
CHANG, SJ
;
LEE, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Light sensitivity of sidegating effect in GaAs MESFET's is investigated by performing two-dimensional numerical simulations on realistic sidegate structures. Mechanism of the light-induced sidegating is identified and compared with alternative mechanisms of sidegating including trap-fill-limited conduction and conduction through the Schottky-i-n(sidegate) structure. Ionization of hole traps in the substrate by capturing the photo-generated holes is found to be the major cause of light-induced sidegating effect which occurs even at very low sidegate voltages. In the presence of the hole traps occupied by holes, the potential distribution in the electron-trap-rich substrate becomes similar to that in the hole-trap-rich substrate, i.e., the negative voltage applied to the sidegate is carried over to the channel-substrate interface.
NUMERICAL-SIMULATION OF SIDEGATING EFFECT IN GAAS-MESFETS
(1993-04-01)
CHANG, SJ
;
LEE, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Two-dimensional simulation of the sidegating effect in GaAs MESFET's has been performed. The result confirms that Schottky contacts on a semi-insulating substrate cause serious high substrate leakage current and drain current reduction in GaAs MESFET's. The threshold behavior in sidegating effect is found to correlate with the conduction behavior of the Schottky-i-n(sidegate) structure when the sidegate is negatively biased. Shielding and enhancement of the sidegating effect by the Schottky contacts have also been studied and the results agree with the experimental findings. Besides, the presence of hole traps in the semi-insulating substrate is found to be essential to the sidegating effect.
NUMERICAL-SIMULATION OF THE HYSTERESIS IN THE SIDEGATING EFFECT IN GAAS-MESFETS - THE EFFECT OF SCHOTTKY CONTACTS
(1992-08-01)
CHANG, SJ
;
LEE, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Two-dimensional simulation of the sidegating effect in GaAs MESFET's has been performed. The result confirms that Schottky contacts on semi-insulating substrate cause serious high substrate leakage current and drain current reduction in GaAs MESFET's. The competition between the currents or biases of the contacts is found to be the cause of the S-type negative differential conductivity (S-NDC) or hysteresis observed when measuring the sidegating threshold.
NUMERICAL-SIMULATION OF THE SUPPRESSION OF SIDEGATING EFFECTS IN GAAS-MESFETS BY ION-BOMBARDMENT
(1993-10-01)
CHANG, SJ
;
LEE, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effect of ion bombardment on sidegating effect in GaAs MESFETs has been studied by two-dimensional numerical simulations. Respective contributions of the bombardment induced electron traps, hole traps and neutral recombination centers to the suppression of sidegating effect in GaAs MESFETs have been studied. The increase of electron traps and the induced neutral recombination centers was found to be the main reason for the reduction of the sidegating effect. The results provide a further support to the sidegating picture in which Schottky contacts on the semi-insulating substrate play an important role.
NUMERICAL-SIMULATION OF THE TEMPERATURE-DEPENDENCE OF THE SIDEGATING EFFECT IN GAAS-MESFETS
(1994-08-01)
CHANG, SJ
;
LEE, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The temperature dependence of the sidegating effect in GaAs devices has been investigated by performing two-dimensional numerical simulations on realistic structures. The less sidegating and the higher sidegating threshold at higher temperatures are found to be caused by the temperature-dependent trapping properties of the deep traps and the difference in increase rate with temperature of the currents in various current paths. These results provide further support lo the sidegating picture in which Schottky contacts on the semi-insulating substrate play an important role.