Abstract
The self-heating effects (SHEs) on the electrical characteristics of the GaN MOSFETs with a stacked TiO2/Si3N4 dual-layer insulator are investigated by using rigorous TCAD simulations. To accurately analyze them, the GaN MOSFETs with Si3N4 single-layer insulator are conducted to the simulation works together. The stacked TiO2/Si3N4 GaN MOSFET has a maximum on-state current of 743.8 mA/mm, which is the improved value due to the larger oxide capacitance of TiO2/Si3N4 than that of a Si3N4 single-layer insulator. However, the electrical field and current density increased by the stacked TiO2/Si3N4 layers make the device’s temperature higher. That results in the degradation of the device’s performance. We simulated and analyzed the operation mechanisms of the GaN MOSFETs modulated by the SHEs in view of high-power and high-frequency characteristics. The maximum temperature inside the device was increased to 409.89 K by the SHEs. In this case, the stacked TiO2/Si3N4-based GaN MOSFETs had 25%-lower values for both the maximum on-state current and the maximum transconductance compared with the device where SHEs did not occur; Ron increased from 1.41 mΩ·cm2 to 2.56 mΩ·cm2, and the cut-off frequency was reduced by 26% from 5.45 GHz. Although the performance of the stacked TiO2/Si3N4-based GaN MOSFET is degraded by SHEs, it shows superior electrical performance than GaN MOSFETs with Si3N4 single-layer insulator.
Highlights
Silicon (Si) is widely used in the semiconductor industry as it is a material with very stable physical properties
high-electron-mobility transistor (HEMT) devices operate in enhancement-mode, the normally off operation is more appropriate for gallium nitride (GaN)-based transistors to target high-voltage power switching applications for fail-safe requirements and to simplify the design of driving circuits
When TiO2 is used alone as a gate-insulator, the high dielectric constant can result in better electrical properties, its small band gap generates a large leakage current compared with other high-k materials
Summary
Silicon (Si) is widely used in the semiconductor industry as it is a material with very stable physical properties. The two-dimensional electron gas (2DEG) formed between AlGaN and GaN layers results in a high switching speed, low on-resistance, large current handling capabilities, and high breakdown voltage [4,5]. It has long been established as a promising candidate for high-frequency operation because the high saturation velocity of the electrons significantly enhances the transport properties [6]. In this study, we compare the DC performance changes in GaN MOSFET using the stacked TiO2/Si3N4 dual- or Si3N4 single-layer insulator depending on whether the SHEs is applied and analyze the operation at a large RF frequency, which is expected to change due to dispersion of temperature, considering the thermal mechanism. For the proposed device structure, we experiment to explore the tendency and sensitivity of the performance change when materials with different thermal conductivities are used as substrates
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