Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing
Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing
复制标题
通过预欧姆凹槽蚀刻和低温退火实现 AlGaN/GaN 异质结构 Ti/Al/Ti/W 无 Au 欧姆接触的机理
DOI：
10.1063/1.4939190
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发表时间：
2015-12-28
影响因子：
4
通讯作者：
Zhang, Bo
中科院分区：
文献类型：
--
作者：
Zhang, Jinhan;Huang, Sen;Zhang, Bo
利用电流-电压、高分辨透射电子显微镜和温度依赖的接触电阻特性，系统研究了AlGaN/GaN异质结低热预算无Au欧姆接触的物理机制。在600 °C的低退火温度下，AlGaN势垒的预欧姆凹陷蚀刻被证明是降低Ti/Al/Ti/W欧姆金属与AlGaN/GaN异质结构之间的接触电阻的有效方法。然而，AlGaN势垒的进一步过度凹陷导致仅侧壁接触到2D电子气沟道，从而降低了接触性能。温度相关的接触电阻测量结果表明，AlGaN/GaN异质结势垒部分凹陷和过凹陷的无Au欧姆接触中，场发射（隧穿）是电流输运的主导机制，而传统的Ti/Al/Ni/Au欧姆接触中，场发射和电子发射都是电流输运的主要机制。
The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN heterostructures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 °C, pre-ohmic recess etching of the AlGaN barrier down to several nanometers is demonstrated to be an effective method to reduce the contact resistance between Ti/Al/Ti/W ohmic metals and AlGaN/GaN heterostructures. However, further over recess of the AlGaN barrier leads to only sidewall contact to 2D electron gas channel and thus degraded contact performance. It is verified by temperature-dependent contact resistivity measurements that field emission (tunneling) dominates the current transport mechanism in Au-free ohmic contacts with AlGaN barrier partially and over recessed, while both field emission and thermionic emission contribute to traditional Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructur...