Browsing by Author "TSAI, JW"

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ANOMALOUS BIAS-STRESS-INDUCED UNSTABLE PHENOMENA OF HYDROGENATED AMORPHOUS-SILICON THIN-FILM TRANSISTORS
(1995-10-23)
TAI, YH
;
TSAI, JW
;
CHENG, HC
;
SU, FC
;
電子工程學系及電子研究所
Thin-film transistors (TFTs) with different silicon nitride (SiNx) gate compositions and various hydrogen concentrations in their amorphous silicon films (a-Si:H) have been stressed with positive and negative biases to realize the instability mechanisms. For both stress polarities, it is found that the threshold voltage shifts significantly increase due to the trap sites in the SiNx gate. As the effects of the trapped charges in the SiNx films are reduced, the anomalous threshold voltage shifts under negative stress voltage are observed. The creation of the states near the conduction band in the a-Si:H films can be enhanced according to the defect pool concept and stimulated by the hydrogen contents in the a-Si:H films, which can be confirmed by the subthreshold swing change. Therefore, the negative threshold voltage shifts caused by the hole trapping in the SiN, gate are positively compensated by the created states, reflecting the turnaround behaviors for the threshold voltage shifts. As for the positive stress, the state creation in the a-Si:H films can be suppressed via the defect pool mechanism and thus the threshold voltage shifts are dominantly affected by the electron trapping in the SiNx gates. (C) 1995 American Institute of Physics.
ANOMALOUS BIAS-STRESS-INDUCED UNSTABLE PHENOMENA OF HYDROGENATED AMORPHOUS-SILICON THIN-FILM TRANSISTORS
(1995-10-23)
TAI, YH
;
TSAI, JW
;
CHENG, HC
;
SU, FC
;
奈米中心
Thin-film transistors (TFTs) with different silicon nitride (SiNx) gate compositions and various hydrogen concentrations in their amorphous silicon films (a-Si:H) have been stressed with positive and negative biases to realize the instability mechanisms. For both stress polarities, it is found that the threshold voltage shifts significantly increase due to the trap sites in the SiNx gate. As the effects of the trapped charges in the SiNx films are reduced, the anomalous threshold voltage shifts under negative stress voltage are observed. The creation of the states near the conduction band in the a-Si:H films can be enhanced according to the defect pool concept and stimulated by the hydrogen contents in the a-Si:H films, which can be confirmed by the subthreshold swing change. Therefore, the negative threshold voltage shifts caused by the hole trapping in the SiN, gate are positively compensated by the created states, reflecting the turnaround behaviors for the threshold voltage shifts. As for the positive stress, the state creation in the a-Si:H films can be suppressed via the defect pool mechanism and thus the threshold voltage shifts are dominantly affected by the electron trapping in the SiNx gates. (C) 1995 American Institute of Physics.
ENERGY-DEPENDENCE OF THE ELECTRON-CAPTURE CROSS-SECTION OF GAP STATES IN UNDOPED A-SI-H FILMS
(1995-02-15)
CHEN, YE
;
WANG, FS
;
TSAI, JW
;
CHENG, HC
;
電子工程學系及電子研究所
Isothermal capacitance transient spectroscopy (ICTS) has been employed to measure the energy dependence of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film for the first time, via the proposed novel structure. For undoped a-Si:H films! experimental results show that the electron-capture cross section of defect levels initially decreases exponentially, reaches a minimum, and then increases exponentially with energy depth measured from the mobility edge of the conduction band. This v-shaped distribution of the electron-capture cross section of continuously distributed defect levels in undoped a-Si:H film is different from that in phosphorous-doped a-Si:H film. This means that mechanisms other than multiphonon emission can be dominant in the electron-capture process in the gap states in undoped a-Si:H film.
INSTABILITY MECHANISMS FOR THE HYDROGENATED AMORPHOUS-SILICON THIN-FILM TRANSISTORS WITH NEGATIVE AND POSITIVE BIAS STRESSES ON THE GATE ELECTRODES
(1995-07-03)
TAI, YH
;
TSAI, JW
;
CHENG, HC
;
SU, FC
;
奈米中心
NOVEL STRUCTURE FOR MEASURING THE DENSITY-OF-STATE DISTRIBUTION OF HIGH-RESISTIVITY SEMICONDUCTOR-FILMS BY ISOTHERMAL CAPACITANCE TRANSIENT SPECTROSCOPY
(1994-12-01)
CHEN, YE
;
WANG, FS
;
TSAI, JW
;
CHENG, HC
;
電子工程學系及電子研究所
A novel structure, metal/high-resistivity semiconductor (HRS)/n-type c-Si substrate with the space charge region (SCR) entirely covering the HRS film and penetrating into the c-Si substrate, has been proposed for determining the density-of-state distribution g(E) of the HRS films via the isothermal capacitance transient spectroscopy (ICTS) method. The structure has been tested and applied to the measurement of g(E) of the undoped hydrogenated amorphous silicon (a-Si:H) film. For undoped a-Si:H film with optical gap E(o) = 1.72 eV, a peak in g(E) is observed at 0.66 eV below the conduction band mobility edge E(c), with the attempt-to-escape frequency of u(n) = 1.61 x 10(13) s(-1). These midgap states are surmised to be correlated with the doubly occupied dangling bond D-.