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Non-Alloyed Submicron Resonant Tunneling Device

IP.com Disclosure Number: IPCOM000034533D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Heiblum, M: AUTHOR [+3]

Abstract

A technique is described whereby high frequency oscillator resonant tunneling devices are fabricated without the use of alloyed ohmic contacts, to produce devices with low leakage currents and low parasitic capacitances. Also discussed is the fabrication with the insertion of undoped etch-stop and spacer layers. In order to fabricate submicron resonant tunneling diodes, transistors and photo-detectors with non-alloyed contacts, the implementation necessitates the addition of a very heavily doped layer on the surface of the structure and the insertion of an undoped layer between the doped electrode and the tunneling barriers. In addition, a pseudomorphic layer with a smaller band gap may be placed between the doped layer and the undoped layer to act as an etch-stop layer. The diagram in Fig.

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Non-Alloyed Submicron Resonant Tunneling Device

A technique is described whereby high frequency oscillator resonant tunneling devices are fabricated without the use of alloyed ohmic contacts, to produce devices with low leakage currents and low parasitic capacitances. Also discussed is the fabrication with the insertion of undoped etch-stop and spacer layers. In order to fabricate submicron resonant tunneling diodes, transistors and photo-detectors with non-alloyed contacts, the implementation necessitates the addition of a very heavily doped layer on the surface of the structure and the insertion of an undoped layer between the doped electrode and the tunneling barriers. In addition, a pseudomorphic layer with a smaller band gap may be placed between the doped layer and the undoped layer to act as an etch-stop layer.

The diagram in Fig. 1 illustrates the structure and the associated bands. Although a double-barrier tunneling structure is shown, the concept can be applied to many similar structures requiring a very shallow ohmic contact along with a large barrier to reduce parasitic conductance through areas in close proximity. Generally, the key to obtaining high frequency operation is in the fabrication of very small devices since a reduction in size reduces the

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parasitic capacitance and also reduces the number of parasitic current paths which shunt the resonant effects.

In addition, if the devices are sufficiently small, quantum-confinement effects may be exploited for various applications. The concept described herein is ideally suited for submicron applications. One of the problems associated with submicron device fabrication is the precise definition of the active area. If alloyed contacts are used, diffusion can increase the size of the active region significantly. However, by using non-alloyed contact material, the contact area can be precisely defined to areas as small as 500 angstroms in diameter. In addition, the metal can be used as an etch mask and small mesas can be fabricated with the same precision. The key to the concept is the coupling of etching with the metal pad definition. By using the alloyed metal as an etch mask, a self- aligned structure is attained. Also, some of the problems associated with non-uniformity of the metal after alloying can be avoided, since pin holes in the metal layer can be a significant problem with alloyed contact m...