[EN]In this work, In0.53Ga0.47As planar Gunn diodes specifically designed for providing oscillations
at frequencies below 30 GHz have been fabricated and characterized. Different types of
measurements were used to define a set of consistent methods for the characterization of the
oscillations that can be extended to the sub-THz frequency range. First, negative differential
resistance and a current drop are found in the I–V curve, indicating the potential presence of
Gunn oscillations (GOs), which is then confirmed by means of a vector network analyzer, used
to measure both the S11 parameter and the noise power density. The onset of unstable GOs at
applied voltages where the negative differential resistance is hardly visible in the I–V curve is
evidenced by the observation of a noise bump at very low frequency for the same applied
voltage range. Subsequently, the formation of stable oscillations with an almost constant
frequency of 8.8 GHz is observed for voltages beyond the current drop. These results have been
corroborated by measurements performed with a spectrum analyzer, which are fully consistent
with the findings achieved by the other techniques, all of them applicable to Gunn diodes
oscillating at much higher frequencies, even above 300 GHz.
