Effects of Static and Repetitive Uniaxial Bending Strains on the Electrical Properties and Trap Characteristics of Flexible Low-Temperature Polysilicon Thin-Film Transistors

Effect of Biaxial Bending Strains on the Electrical Characteristics of Flexible Low-Temperature Polysilicon Thin-Film Transistors

Strain distribution and electrical characteristics of flexible low-temperature polysilicon thin film transistors under biaxial bending

Abstract This paper investigates the strain distribution of flexible p-channel low temperature polycrystalline silicon thin film transistors under biaxial bending. The strain distribution of LTPS TFTs under different bending conditions is analysed by finite element analysis. 𝛆r and 𝛆θ are essentially equal and constant within the load ring. The finite element analysis shows that when the biaxial bending strain condition is 2.5%, the strain distribution is mainly concentrated at the contact angle between the electrode and the oxide layer. This strain is significantly greater than the overall strain of the device, which is the main reason for the bending performance of the device. We found that under biaxial bending, the threshold voltage shifts towards the negative axis as the biaxial strain increases. Within this strain range, these electrical properties are evident under biaxial strain conditions. Comparing theoretical threshold voltage shifts based on energy band changes with experimental results under biaxial strain, it was found that changes in trap density should also contribute to the threshold voltage shift.

Wake-up effect in Hf_0.4Zr_0.6O₂ ferroelectric thin-film capacitors under a cycling electric field

We examined the wake-up effect in a TiN/Hf0.4Zr0.6O2/TiN structure. The increased polarization was affected by the cumulative duration of a switched electric field and the single application time of the field during each switching cycle. The space-charge-limited current was stable, indicating that the trap density did not change during the wake-up. The effective charge density in the space-charge region was extracted from capacitance–voltage curves, which demonstrated an increase in free charges at the interface. Based on changing characteristics in these properties, the wake-up effect can be attributed to the redistribution of oxygen vacancies under the electric field.

Study of traps in low-temperature polysilicon thin film transistors using a current transient method

Abstract The trap characteristics of low-temperature polysilicon thin film transistors (TFTs) are studied using a current transient method that is based on the trapping and detrapping of charge carriers from the trap sites in the device. Analysis of the measured current transient curve allowed three types of detrapping behavior to be identified, each of which displayed a different time constant, activation energy, and spatial position. This current transient method can be integrated into the negative bias temperature instability stress test used for the reliability study. The peak amplitudes of the traps increase because of the stress applied in the test, thus demonstrating that the degradation mechanism of the TFTs is closely related to changes in the traps in these devices.

Research on the Wake-up Effect of Ferroelectric HfO2-ZrO2 Thin Films

Abstract The appearance of ferroelectric (FE) and anti-ferroelectric (AFE) properties in HfO2-based thin films is highly intriguing in terms of both the scientific context and practical application in various electronic and energy-related devices. Interestingly, these materials showed a “wake-up effect”, which refers to the increase in remanent polarization with increasing electric field cycling number before the occurrence of the fatigue effect. The appearance of ferroelectric (FE) and anti-ferroelectric (AFE) properties in HfO2-based thin films is highly intriguing in terms of both the scientific context and practical application in various electronic and energy. In this paper, we have conducted an in-depth study on the relationship between the Wake-up effect in HfO2-based films and oxygen vacancies.