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As a transmitter power amplifier (PA), the electrical output characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs) are closely related to the drain current versus drain voltage (${I}_{d}$ – ${V}_{d}$) characteristics. Any abnormalities in the ${I}_{d}$ – ${V}_{d}$ characteristics will seriously affect device performance. Therefore, many groups have investigated the kink effect of GaN HEMTs. One of the commonly used measurement methods of the kink effect is the ${I}_{d}$ – ${V}_{d}$ forward and reverse sweep. In this study, we used the same method for Al2O3/Si3N4–AlGaN/GaN metal–insulator–semiconductor HEMT (MIS HEMT) devices. We found that not only did the kink effect occurred but ${I}_{d}$ also increased abnormally during the reverse sweep and after a series of electrical measurements. At the end of the forward sweep, impact ionization caused by a high ${V}_{d}$ generated electron–hole pairs and some holes accumulated under the gate region, which caused the negative shift of the threshold voltage (${V}_{\text{Th}}$), leading to an abnormal increase in ${I}_{d}$ during the reverse sweep. [ABSTRACT FROM AUTHOR]

This study compares the capacitance–voltage (C–V) characteristics in silicon–germanium (SiGe) metal-oxide-semiconductor capacitances with and without a silicon oxide capping layer. The SiGe channel with the silicon oxide capping layer exhibits an improved C–V property at room temperature but has an abnormal shift and depression at low temperature (77 K). We determined that the threshold voltage shift was induced by the Fermi-level when ambient temperature was changed. The additional silicon capping layer was responsible for introducing defects resulting in depression and hump in the C–V measurements. Such a phenomenon is mainly caused by the different distribution of defects, which was established by modifying the alternating current pulse amplitude during the C–V measurement. [ABSTRACT FROM AUTHOR]

In this letter, a study of physical mechanisms is introduced to describe an abnormal phenomenon in transfer characteristics while p-type low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) were subjected to a negative bias temperature stress (NBTS) in an illuminated environment. In general, under NBTS, the transfer characteristics exhibits a negative shift of threshold voltage and a degradation of subthreshold swing. Here, however, experimental results reveal that the degree of degradation is different after NBTS is applied to poly-silicon TFTs in a darkened and in an ultraviolet condition. This variation is mainly a result of the light-generated electrons recombining with the inversed holes, and leading to a lower degree of degradation. Moreover, we found that the influence of the UV light is an edge effect at different channel lengths. This letter investigates the illumination effect in LTPS TFTs during NBTS, and the phenomenon is clarified by electrical measurements and by trap state extraction. [ABSTRACT FROM AUTHOR]