Negative conductance of diodes on gallium nitride microcathodes

Small-signal negative conductance of a diode on AlGaN micro-cathode, which results from delay of both processes - electron emission and its transit in a vacuum layer, has been studied theoretically. Its periodic dependence on both of delay angles leads to a multiband structure of diode negative conductance spectrum, when the upper angle of emission delay in the spectrum exceeds the same of a transit delay. Owing to sufficiently great electric field values and electron velocity in vacuum the negative conductance of the diode is in terahertz frequency range. The longer the emission delay time, the lesser its value and diode optimal frequency are.