1. Introduction

Among the microwave and MM-wave solid-state devices, IMPact Avalanche Transit Time c 
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w32!z,+3¥ er. Most of the current research activities for MM-wave systems are focused on the design and development of IMPATT devices at MM-wave window frequencies, i.e., 35, 94, 140, 220 GHz, where atmospheric attenuation is relatively low. These devices are finding important applications in tracking radars, missile guidance, battle field communication, collision 2+% \*!z /5/0!)z \* z . %+)!0!./^z 
z %+ !/z/! z +\*z %\_z/\_z \*z\$2!z!!\*z!4¥ perimentally realized to provide sufficient power at MM-wave frequencies. For realizing higher RF power (PRF) from an IMPATT device, one should choose a semiconductor material that has higher value of critical electric field (Ec), saturated drift velocity (vsdz\z0\$!.)(z+\*¥ ductivity (K), since PRF from an IMPATT device is proportional to Ec <sup>2</sup> .vs 2 ^z\$!z!4!((!\*0z)¥ terial properties of WBG semiconductors suggest that WBG semiconductor based IMPATT devices are the future MM-wave sources. With the advent of new technologies for growth of %z .5/0(/\_z .!/!.\$!./z .!z /\$+3%\*#z .!\*!3! z%\*0!.!/0z%\*z !4,(+.%\*#z 0\$!z ,+//%%(%0%!/z +"z !4¥ 0.0%\*#z)+.!z,+3!.z".+)z%w/! z 
z !2%!/^z\$!z!4,!.%)!\*0(z.!/!.\$z+\*z0\$!z !¥ velopment of SiC-IMPATTS is underway. On the other hand, IMPATT device technology based on Si is well established over a wide frequency range. The authors have therefore chosen Si/SiCbased hetero-structure IMPATT diodes, to simulate the large signal properties of the device at W-band (75-110GHz). The authors have developed a generalized technique based on self-consistentmodel for large-signal simulation of SiC DDR IMPATT devices.

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/z\* z+0\$!.z\*!#0%2!z.!/%/0\*!z !2%¥ ces are reported in the literature [1-5]. Earlier reported large-signal modelling are basically analytical modelling of *Read-diodes* with some simplifications and restrictive assumptions, such

© 2013 Mukherjee; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Mukherjee; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

/\_z!-1(z..%!.z2!(+%0%!/\_z%+\*%60%+\*z.0!/z+"z!(!0.+\*/z\* z\$+(!/\_z,1\*\$! z0\$.+1#\$z !,(!¥ tion layer boundaries, non-inclusion of mobile space charge effects. Consequently in their analysis, the generated power increases monotonically with the increasing RF amplitudes i.e. those analyses do not exhibit saturation effects and this constitutes an important limitation in applying those type of models. The authors have assumed a sinusoidal current at the input of the Si/SiC double drift device and obtained the corresponding voltage response to calculate 0\$!z !2%!z%),! \*!^z \*z0\$!z,.!/!\*0z,,!.z0\$!z10\$+.z\$/z"+.)1(0! zz/%),(!z\* z#!\*!.(¥ ized method for large-signal simulation of Si/SiC IMPATTs at 94 GHz based on current excitation at the input of the device. The large-signal impedance as a function of frequency has been obtained by considering the fundamental frequency and higher harmonic terms.

power output as well as other important properties of the device at larger amplitudes of RF signal. A drift-diffusion model has been used for the large-signal analysis. A time varying electric field is assumed in the form, iV DVi *<sup>p</sup>* BV' *<sup>x</sup>* i *<sup>p</sup>* -#(V Mq.NV BV' *<sup>x</sup> <sup>2</sup>* i *<sup>p</sup>* -#(V M:q.NV B*………*, where i *<sup>p</sup>* is the DC peak electric field and ' *<sup>x</sup>* is the modulation factor. The value of ' *<sup>x</sup>* can be varied to study the effect of field modulation on the large signal properties of IMPATT device. The physical phenomena take place in the semiconductor bulk along the symmetry

High-Power Hexagonal SiC Device: A Large-Signal High-Frequency Analysis

http://dx.doi.org/10.5772/52982

339

\$!z "1\* )!\*0(z !2%!z!-10%+\*/z%^!^\_z+%/+\*j/z!-10%+\*z c!-10%+\*z cDdd\_z+\*0%\*1%05z!-1¥ 0%+\*/zc!-10%+\*/zcEd\zcFddz\* z1..!\*0z !\*/%05z!-10%+\*/zc!-10%+\*/zcGd\zcHddz%\*2+(2%\*#z)+¥ bile space charge in the depletion layer are simultaneously solved under large-signal condition 5z1/%\*#z,,.+,.%0!z+1\* .5z+\* %0%+\*/z5z1/%\*#zz +1(!z%0!.0%2!z"%!( z)4%)1)z+)¥

puter method described below. The fundamental device equations are given below.

( ) ( ( ) ( )) , , , *D A d xt <sup>q</sup> N N p xt n xt dx*

(1)

axis of the mesa structure of IMPATT diodes.

Figure 1. One-dimensional model of DDR IMPATT device.

 
