High Power Low Noise Pt-Schottky Baritt Diodes

The fabrication of Pt-Schottky Baritt diodes is described. Output power as high as 152 mW at 8.6 GHz has been obtained with an efficiency of 2.3 %. The highest efficiency of the diodes is 3 %. The signal to noise ratio is 150 dB and 100 dB for AM and FM noise, respectively. Minimum noise measure of 17 dB single sideband has been achieved. In Baritt diodes a negative rf-resistance can be obtained by barrier injection and transit time delay which make them applicable for amplifiers and oscillators in the microwave region. Because of the simple fabrication and low noise behaviour they have their own place between Impatt diodes and Gunn elements. The most commonly used structures for Baritt diodes are p+np+, p+n¿p+ and metal np+. The highest output powers achieved so far are 115 mW at 6.3 GHz and 85 mW at 8 GHz for p+n¿p+ and p+np+ structures, respectively [1,2]. The maximum efficiency of 4 % could be obtained by using a n+ip¿n+ structure [3] which is rather difficult to fabricate. However, these diodes achieved only relatively low output power of about 13 mW at 7.5 GHz. In X-band the best efficiency attained is 2.6 % from p+np+ structures [2]. Schottky Baritt diodes have been producing lower output power and lower efficiency so far as compared to conventional diffused structures under similar conditions. In this paper the experimental results of Pt-Schottky Baritt diodes are reported showing considerable improvements over the earlier ones and also over diffused diodes.