Improved small-signal analysis of the quantum-well injectiontransit time diode

Two improved methods for calculating the small-signal impedance of the quantum-well injection transit time diode are discussed. The first extends the traditional analysis to include carrier velocity transient effects, producing an analytical expression from which optimum injection conductance and drift angle can be found. The second method includes the effects of both nonuniform carrier velocity and diffusion, casting the expression for impedance in terms of a double integration that is evaluated numerically. A lumped-element model that closely duplicates the impedance found by the numerical method is developed. A graphical means that allows the generation of the lumped-element model from the DC negative resistance and knowledge of the diode structure is provided. The more sophisticated models developed should be useful in device design, in evaluation of mounting and packaging schemes, and for suppression of unwanted oscillations