氧化镓（β-Ga₂O₃）以其4.9 eV的大能带隙、8MV/cm的高击穿电场以及优异的光电特性而著称。这些特性使其在高频技术、通信和光电子等领域展现出极大的应用潜力。基于氧化镓制作的金属氧化物场效应晶体管（MOSFET）能够实现优异的器件性能。目前β-Ga₂O₃ MOSFET还存在终端结构设计单一、设计性能较差、增强型难以实现等问题。针对上述问题，设计了源、栅、漏和源-栅复合场板，栅台面以及栅台面/栅场板凹槽等多种终端结构，并对其进行参数优化。研究重点在于探讨器件的终端结构设计及参数优化对器件特性的影响，主要分析了击穿电压、导通电阻、阈值电压和功率品质因数等关键参数。具体工作如下：

1、研究了β-Ga₂O₃ MOSFET器件常规和场板终端结构的性能。首先设计了一款栅长2 μm的β-Ga₂O₃ MOSFET作为常规结构，接着对其参数进行优化，发现当栅长为3 μm时，击穿电压达到3099 V，此时功率品质因数为769.42 MW/cm²，在此基础上设计了源场板、栅场板、漏场板、源-栅复合场板四种不同终端结构结构。实验表明，引入场板终端对β-Ga₂O₃ MOSFET器件的饱和漏电流、导通电阻和峰值跨导影响不大。但在外加2500V的源漏电压下，峰值电场由常规结构的6.76 MV/cm降至场板终端的5.86 MV/cm、6.19 MV/cm、5.90 MV/cm和5.16 MV/cm。同时引入场板终端结构使器件的阈值电压显著提高。

2、设计了新型的带有漏场板的栅台面终端结构的β-Ga₂O₃ MOSFET。在常规结构的基础上，探究了不同的栅台面倾角对器件性能的影响。实验结果显示，当倾角为4°时，相较于常规结构，导通电阻降低了12.50%为90.66 Ω·mm，击穿电压提升了68.39%达到了3095 V。通过优化新型栅台面终端器件结构的参数，发现当台面厚度为1.2 μm时，器件的击穿电压可达到4827 V，功率品质因数高达1914 MW/cm²。

3、设计了一款高功率品质因数的增强型栅台面凹槽结构的β-Ga₂O₃金属氧化物场效应晶体管(MOSFET)。为了实现更加优异的增强型β-Ga₂O₃ MOSFET，提出了栅台面凹槽终端结构的β-Ga₂O₃ MOSFET，并设计了一组栅场板凹槽作器件作为对照组。研究在不同的栅凹槽深度、不同的外延层掺杂浓度及不同栅氧介质下器件的性能，发现当凹槽刻蚀深度为110 nm时，两个器件均实现增强型。当外延层的刻蚀深度为200 nm时，栅台面凹槽的比通电阻下降到9.76 mΩ·cm²。当外延层掺杂浓度为3×10¹⁷ cm^-3时，栅台面凹槽的峰值跨导达到了50.58 mS/mm。同时发现栅氧介质HfO₂可以明显提升β-Ga₂O₃ MOSFET的饱和漏电流和功率品质因数，而栅氧介质Al₂O₃可以提升器件的阈值电压。

Gallium oxide (β-Ga₂O₃) is recognized for its substantial bandgap of 4.9 eV, exceptional breakdown strength of 8 MV/cm, and superior optoelectronic characteristics, which endow it with significant potential applications in high-frequency technologies, Communication and Optoelectronics. Gallium oxide-based metal oxide semiconductor field-effect transistors (MOSFETs) exhibit superior device performance. Currently, there are challenges in the design of terminal structures for β-Ga₂O₃ MOSFETs, leading to subpar design performance and a predominant focus on depletion-mode devices, making enhancement-mode devices difficult to realize. Addressing these issues, this study focuses on the design and optimization of terminal structures for β-Ga₂O₃ MOSFETs, including source field plates, gate field plates, drain field plates, composite field plates, gate mesa, and gate trench structures. The objective of this study is to examine how the design of terminal structures and the optimization of parameters influence device properties. It focuses on a detailed examination of critical parameters including breakdown voltage, on-state resistance, and the power figure of merit. The following specific tasks were performed:

1. The performance of β-Ga₂O₃ MOSFET devices with conventional and field-plate terminals was investigated. Initially, a β-Ga₂O₃ MOSFET with a gate length of 2 μm was designed as a conventional structure. Subsequently, the parameters were refined, revealing that the breakdown voltage escalated to 3099 V, a doubling when the gate length was expanded to 3 μm, with a commendable power figure of merit at 769.42 MW/cm². Based on this, four different terminal structures, including source field plate, gate field plate, drain field plate, and source-gate composite field plate, were designed. The findings indicated that incorporating these field-plate terminals marginally affected the saturation drain current, on-state resistance, and peak conductance of the β-Ga₂O₃ MOSFET. When a voltage of 2500 V was applied across the source and drain, the peak channel electric field of the β-Ga₂O₃ MOSFET witnessed a reduction from 6.76 MV/cm in the standard structure to 5.86 MV/cm, 6.19 MV/cm, 5.90 MV/cm, and 5.16 MV/cm in the respective field-plate terminal structures. The incorporation of field plate terminal structures noticeably elevated the threshold voltage of the devices.

2. This paper introduces a novel β-Ga₂O₃ MOSFET with a terminal structure featuring a leakage field plate. Through the alteration of the gate step profile incorporating diverse angles, it was discovered that the step angle of 4° yielded a 12.50% decrease in on-state resistance down to 90.66 Ω·mm and a 68.39% enhancement in breakdown voltage reaching up to 3095V, in comparison to the control structure. By fine-tuning the parameters of the innovative terminal device architecture, the breakdown voltage achieved a high of 4827V when the step thickness was 1.2 μm, and the power quality factor was remarkable at 1914 MW/cm².

3. An optimized β-Ga₂O₃ MOSFET featuring an advanced gate-mesa trench architecture and superior power figure of merit has been engineered.In order to achieve an even superior enhanced β-Ga₂O₃ MOSFET, a β-Ga₂O₃ MOSFET with a gate-mesa trench terminal structure was proposed, and a set of β-Ga₂O₃ MOSFETs with a gate field-plate trench terminal structure was designed as a control group. The functionality of devices was evaluated across a range of gate mesa depths, epitaxial layer doping levels, and gate oxide materials. Results indicate that both devices transitioned to enhancement mode operation when the trench depth reached 110 nm. Moreover, a reduction in the epitaxial layer etching depth to 200 nm was found to enhance the gate-mesa trench's specific on-resistance to 9.76 mΩ·cm². At a doping concentration of 3×10¹⁷ cm^-3 for the epitaxial layer, the gate-mesa trench exhibited a peak transitance of 50.58 mS/mm. Concurrently, the use of HfO₂ as the gate oxide material was found to markedly augment the saturation drain current and power figure of merit of β-Ga₂O₃ MOSFETs, whereas Al₂O₃ as the gate oxide material resulted in an elevated threshold voltage for the device.

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