High Performance Buffers for RF GaN Electronics

AlGaN/GaN高电子迁移率晶体管（hemt）是未来低碳经济中功率调节应用以及高效军用和民用微波系统的关键使能技术。GaN-on-Si作为一种低成本、中等性能的技术平台具有很高的吸引力，已被证明甚至可用于w波段。硅的主要缺点是低带隙和电阻损耗衬底，特别是在适度升高的温度下，硅在外延过程中容易无意中掺杂镓，导致射频损耗，以及与目前使用的4”SiC生长衬底相比，硅的相对低导热性导致的功率处理受到一定限制。然而，成本效益是巨大的，允许6英寸甚至8英寸的大批量晶圆加工。在新兴的GaN-on-Si功率开关市场的推动下，6英寸GaN-on-Si外延已经可用，但它针对高压、开关模式操作进行了优化。使用GaN-on-Si提高射频功率放大器（PA）效率是本提案的重点，它将降低晶体管温升，减少衬底损耗，并提供低成本的高性能技术，因为它可以降低晶体管温升和衬底损耗。所需的进步是优化RF特定GaN-on- si晶体管架构，这需要详细了解通过铁，碳和碳/铁共掺杂引入这些器件的GaN缓冲中的电子陷阱，这是目前所缺乏的。本提案的主要目的是使用GaN缓冲器的新型外延设计来控制和模拟器件的电容和电导，因为这是提高射频放大器的效率、增益和线性度的关键。

AlGaN/GaN high electron mobility transistors (HEMTs) are a key enabling technology for future power conditioning applications in the low carbon economy, and for high efficiency military and civilian microwave systems. GaN-on-Si is highly attractive as a low cost, medium performance technology platform which has been proved to be usable even up to the W-band. The main down-sides of Si are the low bandgap and hence resistive lossy substrate especially at modest elevated temperatures, the vulnerability of the Si to unintentional doping with gallium during epitaxy causing RF losses, and the somewhat restricted power handling resulting from the relatively low thermal conductivity of the Si compared to the 4" SiC growth substrates currently used. However the cost benefits are dramatic allowing 6" or even 8" high volume wafer processing. 6" GaN-on-Si epitaxy is already available driven by the emerging GaN-on-Si power switch market, however it is optimised for high voltage, switched-mode operation. Improved RF power amplifier (PA) efficiency using GaN-on-Si, which is the focus of this proposal, would reduce the transistor temperature rise, reduce the substrate losses and deliver a low-cost high-performance technology as it would reduce the transistor temperature rise and reduce the substrate losses. The advance that is required is an optimised RF specific GaN-on-Si transistor architecture, which requires detailed understanding of electronic traps introduced into the GaN buffer of these devices by iron, carbon and carbon/iron co-doping, which is presently lacking. The key aim of this proposal is to control and model the device capacitances and conductances using novel epitaxial design of the GaN buffer, as this is key to delivering improved efficiency, gain and linearity in RF amplifiers.