Engineered substrates technology
Rare earth oxides: A great intermediary for GaN on large-area silicon
GaN-on-silicon products will become far more competitive when processing is carried out at fully depreciated 200 mm silicon fabs. This requires the use of very flat wafers,which can be formed through the introduction of rare oxide epi-layers that can also enhance the performance of LEDs, transistors and solar cells, say Michael Lebby, Andrew Clark and Guoying Ding from Translucent.
T
o fulfil the unrelenting drive for cheaper consumer products, scientists need to develop and introduce new materials that can slash the cost of semiconductor devices. This is especially true for GaN-based technologies – these can form a wide range of devices at costs that will get more and more competitive when epitaxial growth is performed on large silicon wafers. Such devices promise to spur the widespread adoption of LED-based lighting, aid the penetration of GaN-based transistors in the power electronics industry, and help the growth of the multi-junction solar cell market that is traditionally making products for satellites, but is now complementing this with devices for terrestrial concentrating photovoltaic systems.
At Translucent of Palo Alto, CA, we are playing a key role in the development of engineered, silicon-based substrates for the manufacture of GaN products. These large-diameter ‘on-silicon’ wafer platforms, which provide a strong foundation for GaN and germanium epitaxial growth, are by no means the only engineered platforms that exist. However, they have a major advantage over many of them, thanks to their silicon base: They can be processed in the high-volume, highly automated 150 mm and 200 mm silicon fabs dotted around the world. This means that they promise to trim the price of electronic devices based on GaN- on-silicon and germanium-on-silicon, which tend to be made on smaller substrates.
In addition, they can be an attractive alternative to sapphire for the growth of LEDs. The GaN LED industry is migrating from 2-inch, 4-inch and 150 mm platforms used today to 200 mm and beyond.
July 2012
www.compoundsemiconductor.net 37
The appeal of our engineered substrates is not limited to their competitive price – they also simplify epitaxy and wafer fab processing. Given the standard tool kits in these large silicon fabs, thin flat wafers are a pre-requisite for automatic batch loading.
One of the first demands from the silicon community, when faced with the request to process wafers featuring GaN or germanium is essentially: “We need flat wafers folks. We are not interested in the quality of your GaN, but if you want us to process them – they had better be flat.”
Silicon is certainly not the only foundation looking to impact these fast growth markets; scaling to 200 mm has been demonstrated in both sapphire and germanium.
However, both these alternatives suffer from cost, fragility, yield and thickness issues, which don’t plague epitaxial structures formed with our engineered substrates.
Figure 1. Comparison of surface unit cells (decreasing left to right)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186