news digest ♦ Telecoms
High-speed SiGe chips and measurements probes can be seen inside a cryogenic probe station in the laboratory of John Cressler and co-workers at the Georgia Institute of Technology (Georgia Tech Photo: Rob Felt)
Although these operating speeds were achieved at extremely cold temperatures, the research suggests that record speeds at room temperature aren’t far off, says John D. Cressler, a professor who led the research for Georgia Tech.
Information about the research was published in February 2014, byIEEE Electron Device Letters. “The transistor we tested was a conservative design, and the results indicate that there is significant potential to achieve similar speeds at room temperature - which would enable potentially world changing progress in high data rate wireless and wired communications, as well as signal processing, imaging, sensing and radar applications,” says Cressler, who hold the Schlumberger Chair in electronics in the Georgia Tech School of Electrical and Computer Engineering.
He adds, “Moreover, I believe that these results also indicate that the goal of breaking the so called ‘terahertz barrier’ - meaning, achieving terahertz speeds in a robust and manufacturable SiGe transistor - is within reach.” Cressler further says the tested transistor itself could be practical as is for certain cold-temperature applications. In particular, it could be used in its present form for demanding electronics applications in outer space, where temperatures can be extremely low.
Cardoso work at a cryogenic probe station at Georgia Tech. (Georgia Tech Photo: Rob Felt)
IHP, a research centre funded by the German government, designed and fabricated the device, a heterojunction bipolar transistor (HBT) made from a nanoscale SiGe alloy embedded within a silicon transistor. Cressler and his Georgia Tech team, including graduate students Partha S. Chakraborty, Adilson Cordoso and Brian R. Wier, performed the exacting work of analysing, testing and evaluating the novel transistor.
“The record low temperature results show the potential for further increasing the transistor speed toward terahertz (THz) at room temperature. This could help enable applications of silicon-based technologies in areas in which compound semiconductor technologies are dominant today. At IHP, B. Heinemann, H. Rücker, and A. Fox supported by the whole technology team working to develop the next THz transistor generation,” according to Bernd Tillack, who is leading the technology department at IHP in Frankfurt (Oder), Germany. Silicon, a material used in the manufacture of most modern microchips, is not competitive with other materials when it comes to the extremely high performance levels needed for certain types of emerging wireless and wired communications, signal processing, radar and other applications.
John Cressler (left) and graduate student Adilson 104
www.compoundsemiconductor.net March 2014
Certain highly specialised and costly materials - such as InP, GaAs and GaN - presently dominate these highly demanding application areas. But silicon-germanium changes this situation. In SiGe technology, small amounts of germanium are introduced into silicon wafers at the atomic scale during the standard manufacturing process, boosting performance substantially. The result is cutting-edge silicon germanium devices such as the IHP Microelectronics 800 GHz transistor. Such designs combine SiGe›s extremely high performance with silicon›s traditional advantages - low cost, high yield, smaller size and high levels of integration and manufacturability - making silicon with added germanium highly competitive with the other materials. Cressler and his team demonstrated the 800 GHz transistor speed at 4.3 Kelvins (-268oC). This transistor has a breakdown voltage of 1.7 V, a value which is adequate for most intended applications. The 800 GHz transistor was manufactured using IHP’s 130 nm BiCMOS process, which has a cost advantage compared with today’s highly-scaled CMOS technologies. This 130 nm SiGe BiCMOS process is offered by IHP in a multi-project wafer foundry service. The Georgia Tech team used liquid helium to achieve the extremely low cryogenic temperatures of 4.3 Kelvins in achieving the observed 798 GHz speeds. «When we tested the IHP 800 GHz transistor at room temperature during our evaluation, it operated at 417 GHz,» Cressler notes. «At that speed, it›s already faster than 98 percent of all the transistors
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