Observation of intrinsic tristability in a resonant tunneling structure

Abstract

A new technique has been developed to probe the region of apparent bistability due to a tunneling resonance in the characteristic of a semiconductor asymmetric double-barrier structure. The measuring circuit uses a voltage supply designed to have a load line with positive slope, equivalent to a voltage source and negative series resistance. The appearance of bistability and hysteresis in the characteristic is an artifact of the conventional measuring technique, which employs a load line with negative slope. The complete characteristic is found to be a continuous Z-shaped curve between 50 and 150 K, corresponding to tristability. Equivalent circuit models for the device and voltage supply predict a narrow range of circuit parameters for which a static operating point exists inside the tristable region.

Lateral current density fronts in asymmetric double-barrier resonant-tunneling structures

“…An active external circuit which simulates a negative external load resistance and reverses the sign of feedback has been implemented experimentally in Ref. 2. We refer to Refs.…”

“…The bistability of a DBRT structure occurs due to the charge accumulation in the quantum well 1,2 . As a result of the electrostatic feedback the potential of the bottom of the well Φ depends not only on the applied voltage u, but also on the built-up electron concentration n (Fig.1).…”

Tunneling spectroscopy of hole plasmons in a valence-band quantum well

“…This is an artefact due to high-frequency oscillations of the current through the circuit, since it is impossible to stabilize the circuit over the entire range of bias, even when the NOR technique is used. 6 However, the circuit is stable elsewhere, particularly in the regions of interest, i.e., the resonant peak and the satellite features beyond it.…”

“…3,4 To explore the region of I(V) where the plasmon satellite occurs requires a circuit with negative output resistance ͑NOR͒. 6 In this paper, we investigate the analogous process of hole tunneling in a p-type RTD, and observe two distinct satellite peaks which we attribute to the excitation of twodimensional ͑2D͒ hole plasmons in the QW. The special interest in studying this type of device is that the band structure of the hole states in the quantum well is more complex 7,8 than that of electrons.…”

“…In this bias range the current is not single valued due to an electrostatic effect associated with space-charge buildup in the quantum well at resonance. 2,6 This gives rise to a ''voltage overhang'' in I(V) which leads to intrinsic current bistability when the RTD is measured with a conventional voltage sweep circuit. 3,4 To explore the region of I(V) where the plasmon satellite occurs requires a circuit with negative output resistance ͑NOR͒.…”