A new approach to obtain multiple peaks in the current-voltage characteristic of a resonant-tunneling (RT) device is demonstrated. The peaks are generated using only the ground state resonance of the quantum well rather than several states, as in conventional RT devices. The separation between the peaks is voltage tunable and also the peak currents can be made nearly equal, which is necessary to use the device in a variety of circuit applications. A functional device operating at 100 K, with two peaks in the I-V has been fabricated. The first practical demonstration of circuits for frequency multiplication by a factor of five, a three-state memory and a 4-bit parity generator, using a single functional RT device each, is also reported. The use of multiple-peak RT devices in these circuits results in an order of magnitude reduction in the number component per function over conventional techniques.

Resonant tunneling device with multiple negative differential resistance: Digital and signal processing applications with reduced circuit complexity

The functional operation of the MOBILE (monostable-bistable transition logic element) has been studied using multiple-input logic gates. The MOBILE uses two resonant-tunneling transistors (RTTs) connected in series and driven by an oscillating bias voltage to produce a mono-to-bistable transition of the circuit. A MOBILE having three input gates with a 1:2:4 width ratio can distinguish all 8 (2/sup 3/) input patterns corresponding to each weighted sum, depending on the threshold value selected by the control gate. The results confirm the realization of the weighted sum threshold logic operation of input signals. >

Weighted sum threshold logic operation of MOBILE (monostable-bistable transition logic element) using resonant-tunneling transistors

A new resonant-tunneling (RT) functional device with two peaks in the current-voltage (I-V) characteristic has been demonstrated. Contrary to conventional RT devices, the peaks are obtained using a single resonance of the quantum well. The peak's separation is voltage tunable and the peak currents are nearly equal, which is important for a variety of device applications. Using a single device, a three-state memory cell has been implemented.

Resonant tunneling devices with multiple negative differential resistance and demonstration of a three-state memory cell for multiple-valued logic applications

The disclosed invention utilizes a homojunction tunneling mechanism of injection into the channel of a modulation doped field effect transistor. The onset of negative differential resistance can be controlled via the gate of the field effect transistor. In one embodiment there is homojunction tunneling within a bipolar field effect structure.

Semiconductor device with controlled negative differential resistance characteristic

Transport of two‐dimensional electrons in a novel double‐quantum‐well (DQW) field‐effect transistor was systematically studied with emphasis on the effect of resonant interaction. By introducing ionized impurities appropriately into one of the QWs, wave‐function‐dependent scattering process was sensitively controlled by the gate voltage Vg. A prominent valley structure was observed in the channel conductance −Vg characteristics at resonance with the peak‐to‐valley ratio of 3 at 4.2 K. This nonlinear characteristic is caused by the deformation of electron wave functions in the DQW and is found to be well explained by the theoretical calculation. The DQW structure can be utilized for both negative transconductance and velocity modulation devices.

Gigantic negative transconductance and mobility modulation in a double‐quantum‐well structure via gate‐controlled resonant coupling

A double channel field‐effect structure is proposed in which the resonant tunneling between states in either part of the channel is employed to control the parallel transport in the channel. Realistic calculations of the conductance in this structure show that one can use it to design a negative transconductance device or as a velocity field transistor with much improved mobility modulation.

B. Vinter

Papers

Tunneling transfer field-effect transistor: A negative transconductance device