Search

anhydride-poly(ethylene glycol) co-polymer (A-PEGCP) has been synthesized from maleic anhydride, poly(ethylene glycol) and bisphenol-A diglycidyl ether without using any organic solvent. The thin films produced from A-PEGCP solution were spin-coated on ITO-coated glass. The nanoparticles are observed in the thin films. It is proposed that the nanoparticle is built by a self-assembly process with bisphenol-A aggregates and poly (ethylene glycol) moieties. The effects of concentration, thermal annealing, excitation wavelength and moisture on the optical and nanostructured characterization of the thin films are investigated in this study. Photoluminescence (PL) spectrum of the thin film on ITO-coated glass has a peak of about 450 nm that extends from 360 to 550 nm under 325 nm excitation. The increase in PL intensity is accompanied by a red shift of PL spectrum as concentration increases. Moreover, the slightly red shift of PL spectrum is also observed as annealing temperature increases. Meanwhile, PL intensity negligibly decreases with annealing temperature. The degradation in PL intensity is apparent due to moisture. The excitation-wavelength dependent photoluminescence (EWDP) is observed in the thin film. UV-Vis absorption spectra of the thin films are red-shifted with concentration due to more molecular aggregation. The highest occupied molecular orbital (HOMO) energy is &minus, 9.52 eV. The optical band-gap energy is 4.09&ndash, 4.44 eV.

In this paper, the characteristics of InP/InGaAs abrupt, setback, and heterostructure-emitter heterojunction bipolar transistors (HBTs) are comparatively investigated by twodimensional simulation analysis. In the setback (heterostructure-emitter) HBT, a thin 50 A undoped In0.53Ga0.47As (n-In0.53Ga0.47As) layer is inserted between n-InP emitter and p+-InGaAs base layers to lower the energy band at emitter side for decreasing the collector-emitter offset voltage. The simulated results exhibits that the abrupt HBT has the largest current gain, the largest collector-emitter offset voltage, and the smallest unity gain cutoff frequency. While, the setback and heterostructure-emitter HBTs exhibit the smallest current gain and offcet voltage, respectively. Consequentially, the demonstration and comparison of the three-type HBTs provide a promise for design in circuit applications.

In this paper, high device linearity and characteristics of an InGaP/GaAs/InGaAs camel-like gate delta-doped p-channel field-effect transistor is demonstrated. The energy band and hole distribution are depicted with respect to the device performance. Due to the npn depletion of the camel-like gate structure, the considerable conduction band discontinuities at n + -InGaP/p-GaAs and p-GaAs/i-In 0.15 Ga 0.85 As heterojunctions, and the good confinement effect for holes in InGaAs quantum well, a large gate turn-on voltage is achieved. The drain saturation current linearly increases with the gate voltage and the high device linearity is illustrated by fitting the drain current versus the gate voltage. The excellent performance of the studied device is promise for linear amplifiers and high-frequency circuit applications.

Carbon incorporation in strained-Si surface channel NMOSFET is investigated. Due to the ∼52% lattice mismatch between silicon and carbon, the channel is expected to have higher strain than strained-Si, indicating that the carrier mobility can be enhanced significantly. There is a ∼40% electron mobility enhancement for incorporated carbon content of 0.25% in strained-Si NMOSFETs compared to unstrained Si channels. The performance of channels with increased strain is not as high as theoretical predictions. This is due to the large Dit at the oxide/strained-Si:C interface and alloy scattering, which degrades carrier mobility enhancement.

The occurrence of the hysteresis-like breakdown (denoted by BD-H) and the minority carrier generation in MOS structures under substrate injection enhanced by the direct illumination treatment in a rapid thermal processing (RTP) are examined in this study. It is generally believed that the oxide breakdown under substrate injection is related to the oxide quality and the minority carrier generation contributed by bulk traps in Si substrate. For the breakdown behavior of MOS devices subjected by substrate injection, we find that the occurrence frequency of BD-H is more for the samples treated by the front-side heating (FH) processing than for those done by the back-side heating (BH) one in RTP. Besides, it is also observed that the gate saturation current is under the influence of the direct illumination processing. Moreover, from capacitance–voltage (C–V) measurements with various frequencies, it indicates that the generation rate of minority carriers is higher for the samples treated by FH processing than for those done by BH one. These results show that not only localized oxide traps but also Si bulk traps are much easy to be created in the direct illumination processing. It is, therefore, clear that the characteristics of MOS structures with ultra-thin oxides are influenced by the direct illumination in RTP.

The metal-oxide-semiconductor (MOS) solar cells with sol-gel derived silicon dioxides (SiO2) deposited by spin coating are proposed in this study. The sol-gel derived SiO2 layer is prepared at low temperature of 450°C. Such processes are simple and low-cost. These techniques are, therefore, useful for largescale and large-amount manufacturing in MOS solar cells. It is observed that the short-circuit current (Isc) of 2.48 mA, the open-circuit voltage (Vos) of 0.44 V, the fill factor (FF) of 0.46 and the conversion efficiency (η%) of 2.01% were obtained by means of the current-voltage (I–V) measurements under AM 1.5 (100 mW/cm2) irradiance at 25°C in the MOS solar cell with sol-gel derived SiO2.

The effect of oxide barrier shape change caused by stress-induced interface trap charges on the low-voltage tunneling current (LVTC) characteristics of ultrathin gate oxide (∼2 nm) is studied in this work. It was found that for an ultrathin gate oxide working in the direct tunneling regime, the LVTC behavior is strongly dependent on the barrier shape of the oxide. After high-field stress, anomalous LVTC phenomenon is observed. There is an invariant point existing in current–voltage curves. For a bias smaller than the value of the invariant point, the gate current decreases with stress time. However, for a bias larger than that, the gate current increases with stress time and then saturates. This phenomenon cannot be explained by conventional trap-assisted tunneling conduction, but by the change of tunneling probability due to barrier shape variation. An interface trap charge model is proposed to explain the observed invariant point mentioned above. From this, one can find the voltage corresponding to the ...

Soft breakdown properties affected by photon energy during rapid thermal post-oxidation annealing (POA) of ultra-thin gate oxide are investigated. Generally, breakdown can be classified into normal hard breakdown (HBD) and soft breakdown (SBD). It was found that the occurrence of HBD and SBD depends on the process and stress field. Samples with front and back sides illuminated by a tungsten–halogen lamp during rapid thermal POA were examined. We find that front side illuminated oxides show easier SBD than back side ones. These results indicate that the photon energy may not only enhance the strength of Si–O bonds to suppress the lateral propagation of breakdown spots, but also to localize defects to form a conductive path of the leakage current. The understanding of the photon effect in rapid thermal POA is useful for controlling the electrical properties of ultra-thin gate oxides.