The two challenges impede the spread of GaN devices across the board is expected to fall avalanche-style prices

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"The GaN wafer 8-size process is expected to be in volume production by 2017-2020, which will significantly reduce the cost of GaN devices by at least 30%." For the cost reductions, Fujitsu Electronic Components (Shanghai) Co., Ltd. Sun Bin, deputy product manager, said the case.

In addition to making the wafers larger, making gallium nitride wafers thinner makes them directly part of the gallium nitride device (or die), producing "substrate-less gallium nitride wafers" is also a low-cost Application of research and development direction. Gallium nitride chip thickness is usually 0.1 mm, the current sapphire substrate to do out of the gallium nitride chip is usually 0.4 mm in thickness, in the course of the necessary "thin" after the package used.

"The high power density characteristics of GaN devices require a good heat dissipation, so the GaN wafers are usually thinned to 0.05-0.1 mm, which also leads to chip welding and assembly difficulties." Cheng Gang told reporters, silicon-based The GaN process has a natural advantage from the proven traditional silicon process, which enables the wafer to be thinner for better thermal conductivity, while the die bonding and assembly are easier to integrate with conventional processes to accommodate a variety of ceramic and plastic packages.

At the same time in the IC packaging and testing, Texas Instruments Asia Pacific analog products, automotive solutions business development director Wu Weiqiang told reporters, traditionally, GaN devices are packaged as discrete devices, driven by a separate driver, this is because the GaN devices and drivers based on Different processing techniques, and may come from different vendors, each package will have the introduction of parasitic inductance wire and lead. The TI introduced LMG3410 new device is used in 8mmx8mm square flat leadless (QFN) package. In order to create a broad market for GaN development space, TI is committed to helping customers simplify the use of GaN devices, and optimize its performance, by the GaN FET and high-performance drive package together in a module to achieve amazing performance. Compared to a discrete GaN solution, the QFN package reduces power loss, component voltage stress, and electromagnetic interference (EMI).

However, it should be noted that, in addition to the cost and supply capacity challenges, GaN in the high-temperature growth and device manufacturing also has a certain degree of obstacles. In the high-temperature growth of GaN materials, GaN heteroepitaxial (using sapphire and SiC as the substrate) technology to grow the GaN single crystal, it can not solve the problem of high heteroepitaxial defect density itself. Cheng Gang told reporters that the defect can be completely GaN substrate to solve, but its productivity and economy may be more difficult to solve the problem. MACOM uses a mature silicon substrate process to replace sapphire and SiC substrate, while ensuring a considerable RF performance, to solve the problem of productivity and economy, the application of GaN into the utility into a great advance.

In the GaN device manufacturing, because GaN is a wide bandgap semiconductor, the polarity is too large, it is difficult to obtain better metal-semiconductor ohmic contact through high doping, which is a difficult problem in GaN device manufacturing. Cheng Gang said that the current access to good ohmic contact is indeed the focus of attention in the industry, there are several areas of research has achieved positive results, such as the use of HEMT doped region for advanced HEMT design, and low temperature ohms Contact to improve the contact surface morphology. MACOM will consider these processes in subsequent new product evolution, but in fact the process of RF GaN chip is sufficient to meet the current commercial market technical requirements.

From the high-frequency high-power devices began to spread to the formation of 5G deployment of industrial support

Overall, driven by market-driven technology and progress, GaN's momentum will be very rapid, so that the view that, GaN materials will gradually become silicon-based MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) and LDMOS Diffusion metal oxide semiconductor) process alternatives. With the gradual opening of the GaN market applications, GaN is expected with silicon carbide, gallium arsenide and other transistor devices launched in different orders of magnitude of market applications.

Cheng Gang told reporters, as the frequency increases, silicon-based LDMOS very difficult to produce the necessary power, bandwidth and efficiency. GaN material will replace LDMOS in the frequency band above 2.5-2.7 GHz, and will play a role in the lower frequency band. If the price of GaN is close to LDMOS, GaAs will play a role in low-frequency, low-power RF applications at higher frequencies until the ripening price of GaN products is sufficient to compete with GaAs. MACOM believes silicon-based GaN technology should be the fastest to deliver high-volume commercial GaN-based RF performance and will gradually replace GaAs and LDMOS.

Wu Weiqiang said that the power switch has been made of silicon MOSFET, but now is being replaced by GaN-FET. This is because the GaN-based switching power transistors enable new power applications, with higher performance and lower losses when operating at higher voltages than previously used silicon (Si) transistors.

In the past few years, Si switch performance has been greatly improved, but in the same size and high pressure, GaN provides a major improvement is unlikely to be achieved Si. Currently, Si-MOSFETs have a significant cost advantage for GaN, but this cost difference will shrink over time, so GaN may replace silicon-based MOSFETs as design problems are gradually resolved.

In fact, the physical properties of a semiconductor material determine the final performance of the end device. Over the past three decades, silicon has dominated power applications. Wu Weiqiang told reporters, with the performance of silicon close to the theoretical limit, the performance improvement has become very limited. As emerging semiconductor materials, in addition to GaN, SiC is also seen as a promising future for high-performance applications candidate materials, GaN, GaAs, SiC can be used for RF applications.

Specifically, in the RF applications, with the 4.5G deployment and the arrival of 5G era, which the higher the wireless frequency band, or even millimeter-wave band there is a further demand, where GaN will be more application advantages, because the 5G application In the case of a millimeter wave at 28 GHz, the GaN device will be more advantageous than the GaAs device in that GaN can emit the maximum power in the smallest unit area to support faster transfer rates.

Sun Bin said that with the arrival of 5G era, GaN high-frequency characteristics of the advantages will be gradually reflected, but the gallium arsenide is still the mainstream of RF devices, GaN suitable for 100 ~ 1200v in the low-voltage devices, RF device applications, silicon carbide relative to the advantages of GaN in 1200v or more high-pressure applications will be better.

“GaN的应用使得高频高带宽高功率无线通讯系统成为可能。”黄靖表示，这使得今后无线通讯系统可以支撑高于现有4G网络一个数量级甚至几个数量级的数据容量。Qorvo已经针对4.5G无线通讯平台发布了业界第一款高效率小尺寸GaN放大器模组，并且对于未来5G无线通讯系统制定了GaN放大器以及射频前端模组的规划。

  而对于GaN在基站中的应用部署，成钢告诉记者，GaN器件在基站的应用会从高频高功率高效率的功率放大器应用开始普及，并逐渐延伸至低频低功率的使用场景。MACOM的硅基GaN技术也会遵循这样的路径发展，特别是最新的4.5G多入多出系统(Massive-MIMO)技术，更可借助硅基GaN特有的集成电路技术形成高集成、低成本的海量供货，迅速拉近5G通讯的部署前景，远期可以和GaN接收机，数字芯片形成模数混合集成电路，适应未来社会对万物互联、人工智能的通讯技术需求。

  可以看到，目前4.5G正成为部署热点，其主力频段主要应用在2.5GHz以上，而在2.5GHz以下频段，LDMOS的Si器件和GaAs仍占有着举足轻重的地位。

  黄靖表示，4.5G中，主力频段集中在2.6GHz-6GHz，GaN在这些频段将毫无疑问的成为最为重要的高效高功率解决方案。1GHz以下频段，今后仍然以LDMOS为主导，在1.8GHz到2.6GHz，随着频率的提高，宽带应用场景的增加，GaN将逐步占据重要地位。整个GaN的市场应用已经开始爆发，并且在今后的3-5年内将实现巨幅增长。

  “GaAs器件将继续用作增益模块和前置驱动器，用于那些深受GaN影响的应用。”Kevin Harrington表示，GaAs将继续在移动/WLAN /蓝牙应用领域占据主导地位，也将继续应用于功率水平不超过1至2W的高频应用。而GaN器件虽然有潜力达到更好的性能，但价格差异仍是GaN的应用瓶颈。对于需要组合使用多个GaAs功率放大器的传统高频应用，GaN器件将会替代GaAs器件，这种趋势具有性能和成本两方面的优势。

  虽然GaN的市场前景光明，但在有些产品应用中，不排除采用LDMOS更为合适。LDMOS获益于几十年的发展进步和市场的扩张，这使其比GaN更为成熟。这使得其在与其它技术竞争时具有成本上的优势，即使是在对成本敏感的无线基础设施市场上也是如此。

  成钢告诉记者，实际上MACOM的硅基GaN技术可以下探到更低无线频段，所以在主要的通讯频段应该可以替换LDMOS，中高频段仍然是GaAs的优势频段，GaN短期内并无强烈动机去替换GaAs。

  不过，成钢也认为，硅基GaN技术因其特有的硅基片特性容易制作，成本低廉以及天生合适与数字芯片集成，形成其独有的集成电路制作可能性，这对在4.5G乃至5G应用上必需的多入多出系统(Massive-MIMO)大数量收发阵列，具有不容忽视的体积和成本优势，所以硅基GaN技术可能会是4.5G乃至5G应用的最佳选择。GaN在射频功率半导体市场的普及已经因为系统供应商的加速采用而形成强烈拉动，更因为硅基GaN技术带来的性能和成本优势而加速普及，预计在2017年到2018年形成爆发式增长，从而为4.5G乃至5G应用的提前部署形成强有力的产业支撑