Browse Prior Art Database

Electronic Devices Based in Tunneling Between Two-Dimensional Systems

IP.com Disclosure Number: IPCOM000036048D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Chang, LL: AUTHOR [+2]

Abstract

Described are electronic devices in which electrons tunnel between two-dimensional wells separated by a potential barrier. Their unusual current-voltage characteristic can be used to perform rectifying, oscillating and switching functions.

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Electronic Devices Based in Tunneling Between Two-Dimensional Systems

Described are electronic devices in which electrons tunnel between two- dimensional wells separated by a potential barrier. Their unusual current-voltage characteristic can be used to perform rectifying, oscillating and switching functions.

Shown in Fig. 1 is a potential profile along the z direction, which represents the conduction band variation of, for example, GaAlAs with varying alloy compositions. The profile will have a square shape if two distinct compositions (e.g., GaAs and Ga1-xAlxAs) are used. For a two-terminal device, only two wells A and B are needed, with a barrier in the middle. The parameters are such that the A- (or B-) well has the two-dimensional ground state at EA (or EB), with an electron density p [EF-EA(or EB)], where EF is the Fermi level and p is the constant density of states. Under applied voltages, say, VA = 0 and VB = V, electrons tunnel from left to right. To conserve both the total energy and the momentum parallel to the interface, electrons can flow only for V = VR such that eVR = W X (EF - EA) - (EF-EB). Since the value of W in principle can be made arbitrarily small and no current can flow at all in the opposite voltage polarity, this represents the situation of an ideal rectifier. The current- voltage behavior is illustrated in Fig. 2, where a current peak at W is shown with a finite width w, arising from fluctuations either in thickness or in composition. The characteristics in Fig. 2 with on- off regions and associated negative resistances lend themselves to operations as oscillators and switching devices.

The structures can be fabricated by modern, sophisticated techniques of thin- film deposition. The contacts can be made in a number of ways. Most commonly, they can be achieved in the parallel direction (x or y), where the device is not active. A...