Grating-Induced Frequency Multiplication in Planar Gunn Diodes

A new oscillation mode has been observed in bulk planar InP Gunn diode devices with integrated metallic gratings. The grating mode oscillation is distinct from the transit mode of normal Gunn diodes. Its characteristics depend on doping concentration: In 1e17/cc material, the grating mode is consistent with the Smith-Purcell mode [1]. In 5e16/cc material, the grating-mode frequency is 5-10 times higher than the transit frequency with comparable power. It is currently believed that the low-doped mode is attributable to the limited-space-charge accumulation (LSA) mode. This work has led to new design concepts which are expected to result in robust 100-300GHz sources by 2016.