Vertical device operation of AlGaN/GaN HEMTs on free-standing n-GaN substrates

Sugimoto, M.; Ueda, Hiroyuki; Kanechika, Masakazu; Soejima, Narumasa; Uesugi, Tsutomu; Kachi, Tetsu

doi:10.1109/pccon.2007.372994

Cited by 16 publications

(15 citation statements)

References 6 publications

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“…Bulk GaN would also be an attractive substrate for devices, as shown by devices developed as early as 2007 by Toyota; 21 however, as mentioned above, GaN substrate wafers are currently only available with diameters up to two inches. This challenge has been taken up in different ways, with continued development of very high quality small wafers using high pressure and temperature by Amano and others 22 alongside various hydride vapor epitaxy-based techniques.…”

Section: The Materials Challengementioning

confidence: 99%

Power electronics with wide bandgap materials: Toward greener, more efficient technologies

et al. 2015

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IntroductionPower electronics is the branch of electronics specifi cally dealing with collecting, delivering, and storing energy, including general and local/commodity energy supplies, by conversion and control of electrical power.1 Specifi c applications range from power supply systems to motor vehicle drives, 2 photovoltaic and fuel cell converters, inverters, and high-frequency heating, 3 among many others. The impact of power electronics has already been signifi cant and is anticipated to be even more so in the future for effi cient energy production and management.As in most other electronics areas, silicon also has been the predominant semiconductor in power electronics to date. However, with wide bandgap materials power electronic components are faster, smaller, more effi cient, and more reliable than their Si-based counterparts. Moreover, they permit the operation of devices at higher voltages, temperatures, and frequencies, 4 making it possible to reduce volume and weight in a wide range of applications. This could lead to large energy savings in industrial and consumer appliances, accelerate widespread use of electric vehicles and fuel cells, and integrate renewable energy into the electric grid.The power electronics market as a whole was about $20 billion in 2012, and power electronics will remain one of the most attractive branches of the semiconductor industry over the next decade. 5 The latest power electronics market forecasts 6 predict an increase of 60% for low-voltage technologies (below 900 V) by the year 2020, accompanied by an approximately 100% market increase for medium (1.2-1.7 kV) and high voltage (2 kV and above) technologies. This implies that the largest market increase in this sector over the next decade (medium and high voltage) will rely on semiconductor technologies beyond silicon (also see article by Okumura in this issue). This can be likened to a second revolution, equivalent to the introduction of large scale fabrication of silicon complementary metal oxide semiconductor (CMOS) technology, which led to the commoditization of electronics and formed the basis of our modern technological era. The power electronics revolution could be setting the basis for a world centered on greener technologies: improved energy conversion effi ciencies, faster switching, and more compact, lighter systems with better thermal management and tolerance will have tremendous impact on industrialization and energy systems, encompassing energy savings, renewable energy systems, and Greener technologies for more effi cient power generation, distribution, and delivery in sectors ranging from transportation and generic energy supply to telecommunications are quickly expanding in response to the challenge of climate change. Power electronics is at the center of this fast development. As the effi ciency and resiliency requirements for such technologies can no longer be met by silicon, the research, development, and industrial implementation of wide bandgap semiconductors such as gallium nitride (GaN) and sil...

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Section: The Materials Challengementioning

confidence: 99%

Power electronics with wide bandgap materials: Toward greener, more efficient technologies

et al. 2015

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“…Toyota and TCRDL showed the world's first 'normally-off vertical AlGaN/GaN HEMTs' (Fig. 28) [15]. Strictly speaking, it is not truly normally-off, and the performance is not yet satisfactory.…”

Section: Toyota Group Research and Development On Wide-bandgap Semicomentioning

confidence: 99%

Present status and future prospects for electronics in electric vehicles/hybrid electric vehicles and expectations for wide‐bandgap semiconductor devices

Hamada

2008

Physica Status Solidi (b)

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1 Issues surrounding automobiles We humans have achieved great cultural developments over the past thousand or more years. Figure 1 shows the changes in the atmospheric CO 2 concentration over the past approximately 1000 years. Together with the increase in the consumption of fossil fuels which began from the industrial revolution in the 18th and 19th centuries, we can also see a sudden rapid increase in the CO 2 concentration. When we look at the 'CO 2 emissions by sector', we see that, in fact, one-fourth of all CO 2 emissions are due to transport. Together with the rapid increase in atmospheric CO 2 concentration, global average temperatures are also rising. The documentary film An Inconvenient Truth described the way that a broad range of large-scale climate changes are occurring, such as the dramatic reduction in Greenland ice over recent years, as also shown in Fig. 2 [1 , 2]. As all are aware, global warming caused by CO 2 and other factors will not only raise sea levels due to the melting of the ice: there are also frightening warnings of large-scale climate change such as increasing numbers of destructive storms resulting from changes in atmospheric circulation. Toyota understands that the rising concentration of CO 2 in the atmosphere is a serious problem.When evaluating the impact of CO 2 generated by automotive fuels and power trains, it is important to evaluate not only the CO 2 generated by consuming fuel, but also the total amount of CO 2 generated from production to consumption -in other words the well-to-wheel CO 2 . Figure 3 shows a comparison of well-to-wheel CO 2 , using the wellto-wheel CO 2 of a gasoline-powered automobile, shown at the top of the bar graph, as '1'. We can see that compared to this, the CO 2 generated by a diesel automobile is 0.75, and the CO 2 generated by a gasoline hybrid is only 0.45. Other examples of substitute fuels, such as bio-fuels, synthetic fuels, hydrogen, and electricity, are also shown. These show the different levels of well-to-wheel CO 2 which result from different materials and production methods. The amount of well-to-wheel CO 2 that is generated by Toyota refers to the ability of users to continuously enjoy the convenience provided by automobiles as 'sustainable mobility'. In order to achieve this, we are carrying out the endless challenge of minimizing the negative aspects of automobiles, such as CO 2 emissions, air pollution, traffic fatalities, and congestion, while maximizing automobile comfort, enjoyment, and excitement. In the area of the environment, we believe that we can come closer to creating the 'ultimate ecovehicle' by increasing the environmental performance of the power train, utilizing new fuels and electrical energy, and integrating hybrid technology into all of the results. In the Toyota Group, we think that power electronics is a key technology for the automotive technology of the future. We have defined SiC and GaN as core items for breakthroughs in power electronics technologies for the future, and we are energetically pursuing resea...

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“…To get rid of such common problems observed in power HEMTs, vertical transistors, current flow from source to drain vertically, could be a promising alternative. The vertical HEMTs (VHEMTs) are advantageous for their lower parasitic inductance, higher blocking voltage, and smaller size [4][5][6][7][8]. The vertical device structure has source and drain electrodes are in opposite planes of a substrate and current flow vertically which helps to reduce the size of device even for high breakdown voltage.…”

Section: Introductionmentioning

confidence: 99%

Optimal design of the multiple-apertures-GaN-based vertical HEMTs with $$\hbox {SiO}_{2}$$ SiO 2 current blocking layer

Shrestha

Chang

2015

J Comput Electron

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Gallium nitride (GaN) based vertical high electron mobility transistor (HEMT) is very crucial for high power applications. Combination of advantageous material properties of GaN for high speed applications and novel vertical structure makes this device very beneficial for high power application. To improve the device performance especially in high drain bias condition, a novel GaN based vertical HEMT with silicon dioxide (SiO 2 ) current blocking layer (CBL) was reported recently. In this paper, effects of the thickness of CBL layer and the aperture length on the electrical and breakdown characteristics of GaN vertical HEMTs with SiO 2 CBL are simulated by using two-dimensional quantum-mechanically corrected device simulation. Intensive numerical study on the device enables us to optimize and conclude that devices with 0.5-µm-thick SiO 2 layer and 1-µm-long aperture will be beneficial considerations to improve the device performance. Notably, using the multiple apertures can effectively reduce the on-state conducting resistance of the device. On increasing the number of apertures, the drain current is increased but the breakdown voltage is decreased. Therefore, device with four apertures is taken as an optimized result. The maximum drain current of 84 mA B Yiming Li at V G = 1 V and V D = 30 V, and the breakdown voltage of 480 V have been achieved for the optimized device.

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Vertical device operation of AlGaN/GaN HEMTs on free-standing n-GaN substrates

Cited by 16 publications

References 6 publications

Power electronics with wide bandgap materials: Toward greener, more efficient technologies

Power electronics with wide bandgap materials: Toward greener, more efficient technologies

Present status and future prospects for electronics in electric vehicles/hybrid electric vehicles and expectations for wide‐bandgap semiconductor devices

Optimal design of the multiple-apertures-GaN-based vertical HEMTs with $$\hbox {SiO}_{2}$$ SiO 2 current blocking layer

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