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<table width="185" border="0" cellspacing="0" cellpadding="0"> <tr> <td><a href="http://www.aciusa.org" target="_blank"><img src="http://www.empf.org/empfasis/archive/images/aci_sm.gif" alt="Go to the ACI website" width="69" height="44" border="0" align="left" longdesc="http://www.aciusa.org"></a></td> <td><a href="http://www.empf.org" target="_blank"><img src="http://www.empf.org/empfasis/archive/images/empf_sm.gif" alt="Go to the EMPF website" width="65" height="44" border="0" align="right" longdesc="http://www.empf.org"></a></td> </tr> <tr> <td colspan="2"><div align="center"> <table width="175" border="0" align="center" cellpadding="0" cellspacing="0"> <tr> <td valign="top"><span class="style1"><span class="style24"><br> In This EMPFasis Issue<br> <br> </span></span></td> </tr> <tr> <td valign="top" style="padding-left:10px"><!-- InstanceBeginEditable name="Article_1" --> <p align="left"><a href="rfsemi.html">RF Semiconductor Devices</a></p> <!-- InstanceEndEditable --></td> </tr> 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href="http://store.aciusa.org"><img src="http://www.aciusa.org/images/lower-pricing-ad.gif" alt="Discount pricing on IPC training course J-STD-001, 610, 600, 7711, 7712" width="150" height="288" border="1"></a> <a href="http://www.empf.org/empfasis/subscribe.htm"> </a> <p class="style9"><script language="JavaScript"> <!-- function random_imglink(){ var myimages=new Array() myimages[1]="http://www.aciusa.org/wwwaci/html/random/boot.gif" myimages[2]="http://www.aciusa.org/wwwaci/html/random/lead.gif" myimages[3]="http://www.aciusa.org/wwwaci/html/random/help.gif" myimages[4]="http://www.aciusa.org/wwwaci/html/random/service.gif" myimages[5]="http://www.empf.org/empfasis/archive/images/subscribe2.gif" var imagelinks=new Array() imagelinks[1]="http://www.aciusa.org/courses/train_boot.htm" imagelinks[2]="http://www.empf.org/empfasis/leadfree.htm" imagelinks[3]="http://www.empf.org/helpline/helpline.htm" imagelinks[4]="http://www.aciusa.org/ana/ana_home.htm" imagelinks[5]="http://www.empf.org/empfasis/subscribe.htm" var ry=Math.floor(Math.random()*myimages.length) if (ry==0) ry=1 document.write('<a href='+'"'+imagelinks[ry]+'"'+'><img src="'+myimages[ry]+'" border=0></a>') } random_imglink() //--> </script></p> </div></td> </tr> <tr> <td colspan="2"><div align="center"><span class="style5">ACI Technologies Inc.</span><br> One International Plaza<br> Suite 600 <br> Philadelphia, PA 19113 <br> (610) 362-1200 <br> <span class="style6">FAX: </span>(610) 362-1290<br> <span class="style6">HELPLINE: </span>(610) 362-1320<br> <span class="style6">WEBSITE: </span><a href="http://www.empf.org">www.empf.org</a><br> <a href="http://www.aciusa.org">www.aciusa.org</a></div></td> </tr> </table> <p>&nbsp;</p> <p><br> <br> </p> <div align="center"> <p align="center" class="style7">Michael D. Frederickson<br> <strong><em>EMPF Director </em></strong><br> <br> Barry Thaler, PhD.<br> bthaler@aciusa.org <br> <strong><em>Empfasis Technical Editor<br> </em></strong><br> Paul Bratt<br> pbratt@aciusa.org <br> <strong><em>Empfasis Editor</em></strong><br> </p> <p align="center" class="style7"><img src="http://www.empf.org/empfasis/archive/images/iab_sm.gif" alt="IAB" width="100" height="52"><br> <span class="style9">Industrial Advisory Board</span><br> <span class="style14"><em>Gerald R. Aschoff</em>, The Boeing Company<br> <em>Dennis M. Kox</em>, Raytheon<br> <em>Gregory X. Krieger</em>, BAE Systems<br> <em>Edward A. Morris</em>, Lockheed Martin<br> <em>Jane Krueger </em>, Rockwell Collins<br> <em>Gary Kirchner</em>, Honeywell<br> <em>Andrew Paradise</em>, Northrop Grumman<br> <em>Richard Kidwell </em>, ITT Industries</span></p> </div> <p align="center" class="style7"><br> </p> </div> </td> </tr> </table> </div></td> <!-- InstanceBeginEditable name="Body1" --><td width="70%" rowspan="2" valign="top"><div class="body_style" id="body_content"> <p align="center"><img src="images/rfsemi.jpg" alt="title"></p> <p class="body_text"><span class="style20">B</span>y maturing and implementing semiconductor device technology, Navy ManTech anticipates a reduction in size, weight and cost of its naval advanced electronic assemblies.</p> <p>Semiconductors are a unique class of materials because they are, by definition, sometimes insulating and sometimes conducting, and practical conditions exist where the material can act in either manner. A key characteristic of a semiconductor material is its crystal structure which relates to its ability to form bonds with itself and other materials. Another key characteristic is its energy band gap which can be described as the minimum amount of energy required to allow charge transport in a semiconductor. In comparison, materials characterized as metals do not have band gaps because they always transport charge.</p> <p>Semiconductor materials are highlighted in the portion of the periodic table shown in Figure 1-1. Elements are arranged by both mass and number of electrons in the outermost energy level. In this region a  rule of eight holds as a common principle dictating the atomic bond nature and bond strength of the element as eight electrons are needed to fill the outermost shell. Semiconductors consist of a crystal lattice of one or more elements and are referred to as binary, ternary, or quaternary compound semiconductors (depending on the number of elements in the basic structure). Silicon has proven to be the ideal elemental semiconductor for electronics since it has four electrons in its outer orbital that form perfect covalent bonds (using all eight electrons) with neighboring Si atoms in a crystal lattice. For radio frequency (RF) applications, the common compound semiconductor materials include GaAs, GaN, SiGe, and InP.</p> <p align="center"><img src="images/fig1-1.gif"></p> <p>The electric potential bandgap of a semiconductor adjusts with the potential of the adjoining material at the semiconductor junction. This interaction is the basis of  bandgap engineering which is the common term for semiconductor device engineering. As device fabrication quality has improved, this physical junction phenomenon has been used to foster real advantages in device applications based on joined combinations of various semiconductors, metals, and insulating materials.</p> <p>Bandgap engineering is employed in the development of all semiconductor transistor devices including the well established field effect transistor (FET) and bipolar junction transistor (BJT). These use a semiconductor interface as a controlled  gate to regulate the path of electrical charge transport. FETs use a voltage controlled gate while BJTs use a current controlled gate. A popular related device to the FET is the metal oxide semiconductor FET, or MOSFET. The MOSFET (Figure 1-2) is similar in design to the FET, but improves output performance with a metal-oxide insulating film that alters the interface at which the charge current travels. The ability of silicon to oxidize and form a stable oxide layer makes this device very popular for Si-based devices.</p> <p align="center"><img src="images/fig1-2.gif"></p> <p>High electron mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) are particularly well suited for the amplification of large microwave signals with better efficiency for low noise applications. They have been used most often in the recent development of monolithic microwave integrated circuits (MMICs) for microwave and millimeter-wave transistors. These devices use heterojunctions of different semiconductor materials for their operation unlike conventional transistors which use junctions of the same material with different dopants (added impurities).</p> <p>HEMT devices (Figure 1-3) are unique for their enhanced carrier mobility induced by the formation of a two-dimensional region of trapped charges at the junction interface. While the more delicate device geometry results in higher cost devices, the electrical property improvements have been of increasing interest for high performance device applications. With recent improvements in epitaxial fabrication methods, these devices have become an increasingly popular alternative for high performance devices.</p> <p>Modern RF systems for military applications commonly use semiconductor devices to support communications, surveillance, and electronic warfare functions. These devices include amplifiers, mixers, multipliers, dividers, phase-shifters, devices for frequency generation, and highly integrated multifunction parts. While the design of these devices may be similar in theory as silicon based devices for electronics applications, critical RF factors such as the operation frequency, bandwidth, and noise isolation tend to favor devices made with compound semiconductor materials for higher frequencies. A common rule of thumb depicted in Figure 1-4 is that silicon based devices are well suited for common RF applications up to the 1-2 GHz range, while at higher frequencies the bandgap advantages of compound semiconductor devices become worth the cost increase related to fabrication.</p> <p>ManTech programs, by definition, support the technology transfer and deployment activities which integrate the present state of the art technology with modern warship and warfighter development. Many current programs involve the integration of high power and high frequency compound semiconductor based devices to increase the range and efficiency of existing RF systems. The R&D engineering team at the EMPF is comprised of experienced professionals with backgrounds in all aspects of semiconductor and RF technology. This experience is leveraged to evaluate new technology effectiveness, efficiency, reliability, and cost concerns with the overall goal of maintaining the U.S. Navy s superior status on the global stage.</p> <p>References</p> <p>1. Losee, Ferril A. RF Systems, Components, and Circuits Handbook. Boston: Artech House, 2005. Print.</p> <p>2. Maiti, C. K., and G. A. Armstrong. Applications of Silicon-germanium Heterostructure Devices. Bristol [u.a.: Institute of Physics Publ., 2001. Print.</p> <p class="body_text"><img src="../../archive/updated/dperez.gif"></p> </div> </td> <!-- InstanceEndEditable --> </tr> <tr> </tr> </table> <br> <table width="100%" border="0"> <tr> <td colspan="2"><div align="center"> <p><em>The EMPF is a U.S. Navy-sponsored National Electronics Manufacturing Center of Excellence focused on the development,<br> application, and transfer of new electronics manufacturing technology by partnering with industry,<br> academia, and government centers and laboratories in the U.S</em></p> </div></td> </tr> <tr> <td class="footer">ACI Technologies, Inc. - - <a href="http://www.aciusa.org">www.aciusa.org</a> - - (610)362-1200</td> <td><div align="right"><a href="http://www.navymantech.com"><img src="http://www.empf.org/empfasis/archive/images/mantech.gif" width="144" height="42" border="0"></a></div></td> </tr> </table> <div align="right"> <!-- Start of StatCounter Code --> <script type="text/javascript" language="javascript"> var sc_project=350643; var sc_partition=1; </script> <script type="text/javascript" language="javascript" src="http://www.statcounter.com/counter/counter.js"></script> <noscript> <a href="http://www.statcounter.com/free_hit_counter.html" target="_blank"><img src="http://c2.statcounter.com/counter.php?sc_project=350643&amp;amp;java=0" alt="hit counter" border="0"></a> </noscript> <a href="http://www.empf.org/sitemap.htm"><em>[site map] </em></a> <!-- End of StatCounter Code --> <!-- Start of StatCounter Code --> <script type="text/javascript" language="javascript"> var sc_project=1902214; var sc_invisible=1; var sc_partition=17; var sc_security="759b802c"; </script> <script type="text/javascript" language="javascript" src="http://www.statcounter.com/counter/counter.js"></script><noscript><a href="http://www.statcounter.com/" target="_blank"><img src="http://c18.statcounter.com/counter.php?sc_project=1902214&java=0&security=759b802c&invisible=1" alt="website statistics" border="0"></a> </noscript> <!-- End of StatCounter Code --> </div> </body> <!-- InstanceEnd --></html>