Reduction of Impact Ionization in GaAs-Based Planar Gunn Diodes by Anode Contact Design
Reduction of Impact Ionization in GaAs-Based Planar Gunn Diodes by Anode Contact Design
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DOI：
10.1109/ted.2011.2177094
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发表时间：
2012-03
影响因子：
3.1
通讯作者：
M. Montes;G. Dunn;A. Stephen;A. Khalid;C. Li-;D. Cumming;C. Oxley;R. Hopper;Martin Kuball
中科院分区：
文献类型：
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作者：
M. Montes;G. Dunn;A. Stephen;A. Khalid;C. Li-;D. Cumming;C. Oxley;R. Hopper;Martin Kuball
通过电致发光(EL)分析研究了GaAs基平面体效应二极管中的碰撞电离，目的是通过接触设计和整形来减小碰撞电离的幅度，从而提高器件的性能和可靠性。与简单的欧姆接触设计相比，二极管欧姆阳极具有悬垂的肖特基延伸(复合阳极接触)的设计显著减少了碰撞电离量。EL结果与蒙特卡罗模拟结果一致，蒙特卡罗模拟表明，由于阳极肖特基扩展下方的电子密度降低，复合阳极接触器件中的碰撞电离减少，一方面削弱了Gunn域电场并减弱了其在阳极边缘附近的变化，另一方面减少了能够通过碰撞电离产生空穴的电子数量。比较了标准阳极接触方法和复合阳极接触方法在射频操作方面的差异，结果表明，在采用复合阳极接触的器件中，输出功率为-5dBm的振荡高达109 GHz，而全欧姆接触器件没有振荡。本文所报道的结果不仅对平面体效应二极管的设计和制造有用，而且对其他器件，如高电子迁移率晶体管，碰撞电离可能导致可靠性的限制也是有用的。
Impact ionization in GaAs-based planar Gunn diodes is studied through electroluminescence (EL) analysis with the aim of reducing its magnitude by means of contact design and shaping, and thus enhance device performance and reliability. Designs in which the diode ohmic anode has an overhanging Schottky extension (composite anode contact) are shown to result in a significantly reduced amount of impact ionization, as compared with a simple ohmic contact design. The EL results are consistent with Monte Carlo simulations, which show a reduced impact ionization in composite anode contact devices due to a reduced electron density beneath the anode Schottky extension that, on the one hand, weakens the Gunn domain electric field and softens its variations near the anode edge, and, on the other hand, reduces the number of electrons capable of generating holes by impact ionization. A comparison between standard and composite anode contact approaches in terms of radio-frequency operation of the devices is made showing oscillations up to 109 GHz with an output power of -5 dBm in devices featuring the composite anode contact and no oscillations from all-ohmic contact devices. The findings reported in this paper may be useful not only for the design and the fabrication of planar Gunn diodes but also for other devices such as high-electron-mobility transistors where impact ionization can result in reliability limitations.