Analysis of the Q Factor, Efficiency, Stability, and the Design of Read Structures in the Nonlinear Range

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Abstract
Using time‐dependent solutions of the avalanche current generalized for unequal ionization rates and velocities of the two charge carriers, compact formulas for the Q and the efficiency of the Read structure are derived, which are valid from zero to very large oscillation amplitudes. A method is developed to properly account for the internal‐field adjustment (which may be variably positive or negative) that is caused by the nonlinearly rectified avalanche‐current component flowing through the drift region. These developments clearly show that the behavior of the Q at intermediate and large signals cannot be correctly derived unless the avalanche analysis retains terms related to both the in‐phase and out‐of‐phase components of the avalanche current. The behavior of Q vs oscillation amplitude is numerically calculated for a successfully operated prototype and compared with experimental observation. These experimental observations in conjunction with the analytical development also permit an interpretation and assessment of the effects due to inhomogeneities in multiplication found in junctions. Design considerations of Read structures are discussed, particularly how various parameters that are critical in optimizing the efficiency and stability may be controlled by design of the electric‐field distribution of the avalanche. It is shown how advantage may be taken of the asymmetry of ionization rates of the two charge carriers to achieve even higher efficiencies than the 30% Read predicted for the case of equal ionization rates. Finally, certain circuit criteria for achieving dynamic stability are discussed and solutions given.