**3. Millimeter-wave properties of Si and GaAs DDR IMPATT diodes**

The various properties of IMPATT diodes based on the fundamental semiconductor materials like Si and GaAs have been found by the simulation method. The properties like DC characteristics, small signal characteristics and noise behaviors have been computed in DDR structures based on Si and GaAs. The details of the results are discussed in the following sections.

### **3.1 DC characteristics**

The computer simulation method [27] has been applied to a DDR structures IMPATT diode based on Si and GaAs and yields the results of different characteristics. The essential DC characteristics such as peak electric field (Emax), breakdown voltage (*V*B), avalanche zone voltage (VA), efficiency (η), avalanche zone width (XA) and ratio of avalanche zone width to total depletion layer width (XA/W) of the designed DDR IMPATTs are obtained from DC simulation.. The analysis of comparative description of the prospects of GaAs for IMPATT diode with reference to Si IMPATT diodes at different operating frequencies such as 94 GHz, 140 GHz

*IMPATT Diodes Based on GaAs for Millimeter Wave Applications with Reference to Si DOI: http://dx.doi.org/10.5772/intechopen.95874*


**Table 3.**

*DC properties of Si and GaAs DDR diodes at 94 GHz, 140 GHz and 220 GHz with design parameter of Table 2.*

and 220 GHz are presented in **Table 3**. At different frequencies all the considered IMPATT diodes show different kinds of behavior.

The breakdown voltage for GaAs IMPATT diode shows the high value over Si IMPATT. This high value of break down voltage produces high RF power output as compared to Si IMPATT. Again, GaAs IMPATT provides more efficiency than Si IMPATT and the efficiency values are given in **Table 3**. The percentage of the ratio of avalanche zone width to total drift layer width (XA/W) for all the diodes structure under consideration increases with higher operating frequencies. Higher value of XA/W describes wider avalanche zone which leads to higher avalanche voltage (VA) and lower drift zone voltage (VD). In case of GaAs-based DDRs XA/W is 42.36% at 94 GHz but it rises to 48.22% at 220 GHz which causes the decrease of efficiency (η) at 220 GHz. But in Si DDRs at 94 GHz, XA/W is 42.7%, whereas it is 45.48% at 220 GHz and this leads to fall in efficiency (η) at higher mm-wave frequencies.
