High power IMPATT diodes utilizing ion implantation

Relatively large amounts of microwave power have recently been observed from impatt diodes fabricated with ion implantation. Boron was implanted into N-type epitaxial silicon to a depth of 0.3µ at 60 Kv to form the p-n junction. The diodes were in the form of a mesa, with appropriate metallurgy for ohmic contacts and heat sinking. The diodes were mounted directly in chip form in a reduced height-waveguide. A sliding short and three tuning screws were used to tune the cavity. The frequency of operation was mainly in X-band. The implanted diodes have shown considerable improvement in performance over diffused diodes fabricated with similar configuration. Measurement of junction temperature for the same input power has shown that implanted diodes run "cooler" than comparable diffused diodes. AM noise measurements made on diffused and ion implanted diodes show an improvement in the signal to noise ratio for the ion implanted diodes. It is worth mention that the microplasma density is considerably smaller for implanted diodes. Utilization of ion implantation facilitates the fabrication of the diodes simply because the depth of penetration of the implanted layer follows the surface contour quite faithfully and thus eliminates the thickness variations due to diffusion. Thus, the main source of irregularity is due to the epitaxial layer thickness with a resultant improvement in yield and operation.