Tajalli Alaleh, Borga Matteo, Meneghini Matteo, De Santi Carlo, Benazzi Davide, Besendörfer Sven, Püsche Roland, Derluyn Joff, Degroote Stefan, Germain Marianne, Kabouche Riad, Abid Idriss, Meissner Elke, Zanoni Enrico, Medjdoub Farid, Meneghesso Gaudenzio
Department of Information Engineering, University of Padova, 35151 Padova, Italy.
Fraunhofer Institute for Integrated Systems and Device Technology IISB, 91058 Erlangen, Germany.
Micromachines (Basel). 2020 Jan 17;11(1):101. doi: 10.3390/mi11010101.
We investigated the origin of vertical leakage and breakdown in GaN-on-Si epitaxial structures. In order to understand the role of the nucleation layer, AlGaN buffer, and C-doped GaN, we designed a sequential growth experiment. Specifically, we analyzed three different structures grown on silicon substrates: AlN/Si, AlGaN/AlN/Si, C:GaN/AlGaN/AlN/Si. The results demonstrate that: (i) the AlN layer grown on silicon has a breakdown field of 3.25 MV/cm, which further decreases with temperature. This value is much lower than that of highly-crystalline AlN, and the difference can be ascribed to the high density of vertical leakage paths like V-pits or threading dislocations. (ii) the AlN/Si structures show negative charge trapping, due to the injection of electrons from silicon to deep traps in AlN. (iii) adding AlGaN on top of AlN significantly reduces the defect density, thus resulting in a more uniform sample-to-sample leakage. (iv) a substantial increase in breakdown voltage is obtained only in the C:GaN/AlGaN/AlN/Si structure, that allows it to reach V > 800 V. (v) remarkably, during a vertical I-V sweep, the C:GaN/AlGaN/AlN/Si stack shows evidence for positive charge trapping. Holes from C:GaN are trapped at the GaN/AlGaN interface, thus bringing a positive charge storage in the buffer. For the first time, the results summarized in this paper clarify the contribution of each buffer layer to vertical leakage and breakdown.
我们研究了硅基氮化镓外延结构中垂直漏电和击穿的起源。为了了解成核层、AlGaN缓冲层和碳掺杂氮化镓的作用，我们设计了一个顺序生长实验。具体来说，我们分析了在硅衬底上生长的三种不同结构：AlN/Si、AlGaN/AlN/Si、C:GaN/AlGaN/AlN/Si。结果表明：(i) 在硅上生长的AlN层的击穿场强为3.25 MV/cm，该值随温度进一步降低。这个值远低于高结晶度AlN的值，这种差异可归因于诸如V型坑或穿透位错等高密度垂直漏电路径。(ii) AlN/Si结构显示出负电荷俘获，这是由于电子从硅注入到AlN中的深陷阱所致。(iii) 在AlN顶部添加AlGaN可显著降低缺陷密度，从而导致样品间漏电更加均匀。(iv) 仅在C:GaN/AlGaN/AlN/Si结构中获得了击穿电压的大幅增加，使其能够达到V > 800 V。(v) 值得注意的是，在垂直I-V扫描期间，C:GaN/AlGaN/AlN/Si堆叠显示出正电荷俘获的证据。来自C:GaN的空穴被困在GaN/AlGaN界面处，从而在缓冲层中实现正电荷存储。本文总结的结果首次阐明了每个缓冲层对垂直漏电和击穿的贡献。
