GREMAN UMR 7347, Université de Tours, CNRS, INSA Centre Val de Loire, 37071 Tours, France.
STMicroelectronics Tours, 37071 Tours, France.
ACS Appl Mater Interfaces. 2023 Feb 15;15(6):8723-8729. doi: 10.1021/acsami.2c21106. Epub 2023 Feb 2.
The fabrication of low-resistance and thermally stable Ohmic contacts is essential for the realization of reliable GaN power devices. In the particular case of p-type GaN, a thin Ni/Au bilayer is commonly used for Ohmic contacts. However, Au metal contacts are quite expensive, are incompatible with the complementary metal oxide-semiconductor foundries, and also have poor thermal stability. Thus, seeking an alternative that is affordable and thermally stable is crucial. In the present study, we investigate Au-free Ohmic contact formation on p-type GaN using a bilayer Ni/Al-doped ZnO (AZO) thin film. Careful studies were focused on identifying the role of process parameters such as annealing parameters: temperature, time, and atmosphere in order to obtain an excellent Ohmic contact on p-GaN. Our results show that the contact resistance can be significantly reduced using a Ni/AZO bilayer with a suitable rapid thermal process. We demonstrate that the specific contact resistance for Ni/AZO on p-GaN can reach the lowest value of 1.85 × 10 Ω·cm for a sample with a 5 nm Ni layer annealed at 500 °C in air for 5 min. Our work demonstrates that the bilayer Ni/AZO contact could be suitable for efficient GaN power diodes or transistors.
为了实现可靠的 GaN 功率器件，制造低电阻和热稳定的欧姆接触至关重要。对于 p 型 GaN 而言，通常使用薄的 Ni/Au 双层来实现欧姆接触。然而，Au 金属接触非常昂贵，与互补金属氧化物半导体（CMOS）制造厂不兼容，并且热稳定性也较差。因此，寻找一种价格合理且热稳定的替代材料至关重要。在本研究中，我们使用双层 Ni/掺铝氧化锌（AZO）薄膜研究了 p 型 GaN 上无 Au 的欧姆接触形成。我们着重研究了确定工艺参数（例如退火参数：温度、时间和气氛）的作用，以便在 p-GaN 上获得优异的欧姆接触。我们的结果表明，使用合适的快速热工艺可以显著降低 Ni/AZO 双层的接触电阻。我们证明，对于在空气中于 500°C 退火 5 分钟的具有 5nm Ni 层的样品，Ni/AZO 对 p-GaN 的比接触电阻可低至 1.85×10Ω·cm。我们的工作表明，双层 Ni/AZO 接触可能适合高效 GaN 功率二极管或晶体管。
