Small-signal performance of a quantum well diode

We study a small-signal performance of a quantum well (QW) diode with triangular emitter and collector barriers providing thermionic electron transport. Analytical expression for the QW diode admittance is obtained from the rigorous self-consistent small-signal analysis. Frequency dependence of the admittance is determined by a characteristic time of recharging of the QW, which is a strong function of temperature and parameters of the QW diode. Conductance as a function of temperature shows a local maximum corresponding to a resonance between a probe signal and recharging processes. Capacitance of the QW diode depends critically on the efficiency of the electron transport through the QW, and can significantly exceed all geometric capacitances associated with the device structure. Experimental data on conductance and capacitance of the QW diode as functions of temperature and frequency can be used to extract the parameters of the QW, such as QW recombination velocity, ionization energy, etc. Analytical analysis of transient currents in the QW diode allows a transparent explanation why an incremental charge-partitioning technique fails to calculate the capacitance even in the low-frequency limit.