Theory of VHF detection and frequency multiplication with space-charge-limited current (SCLC) silicon diodes

Abstract

A non-linear theory of transit-time effects upon VHF detection and frequency multiplication with SCLC silicon diodes, is put forward. Diffusion is neglected and carrier mobility is assumed to be field-independent. The theory applies to the SCLC resistor ( n + νn + structure) and the punch-through diode ( n + πn +). An analytical theory for relatively small signal-amplitudes is developed. Then, computer calculations yield the frequency and bias dependence of the detected current and the second-harmonic amplitude. It is shown that by properly biasing the n + νn + device (the transition region between the ohmic and square-law regions), the detected current is almost frequency-independent up to extremely high frequencies. On the other hand, the transit-time effects upon the detection characteristics of the punch-through diode are by far more important and limit the device usefulness to frequencies below the transit-time frequency. The amplitude of the second harmonic strongly depends upon frequency for both n + νn + and n + πn + structures.