Design considerations of low-noise high-efficiency silicon IMPATT diodes

The noise and efficiency of p
⁺
-n
1
-n
2
-n
⁺
and n
⁺
-p
1
- p
2
-p
⁺
high-low silicon IMPATT diodes have been studied as a function of doping ratio n
1
/n
2
or p
1
/p
2
. In contrast to GaAs IMPATT diodes whose efficiency can be improved with some degradation of noise performance, both the efficiency and noise of Si IMPATT diodes can be improved. As an example, for a 6-GHz silicon n
⁺
-p
1
-p
2
-p
⁺
IMPATT structure with a doping ratio of 10, the efficiency is 21 percent and the incremental noise as compared to a uniformly doped structure is about -6 dB. These results indicate that silicon high-low structures can compete favorably with GaAs structures in both efficiency and noise performances.