Browse Prior Art Database

New Method for Diffusing Species by Using Solutions

IP.com Disclosure Number: IPCOM000042305D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Potemski, RM: AUTHOR [+2]

Abstract

A dopant is diffused into a solid semiconductor material by placing a permeable membrane on the semiconductor surface and bringing a liquid solution into contact with the permeable membrane. The liquid solution is a saturated solution with respect to the solid semiconductor material and has dopant added thereto. If the solution is perfectly saturated at the precise temperature used, the dopant diffuses from the liquid phase into the solid phase (or in the other direction) without any tendency for the solid phase to dissolve or grow. Without the permeable membrane there would be solid phase growth or dissolution when the temperature changes even by a small amount from the precise temperature at which the solution is precisely saturated.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 51% of the total text.

Page 1 of 2

New Method for Diffusing Species by Using Solutions

A dopant is diffused into a solid semiconductor material by placing a permeable membrane on the semiconductor surface and bringing a liquid solution into contact with the permeable membrane. The liquid solution is a saturated solution with respect to the solid semiconductor material and has dopant added thereto. If the solution is perfectly saturated at the precise temperature used, the dopant diffuses from the liquid phase into the solid phase (or in the other direction) without any tendency for the solid phase to dissolve or grow. Without the permeable membrane there would be solid phase growth or dissolution when the temperature changes even by a small amount from the precise temperature at which the solution is precisely saturated. The permeable membrane acts to prevent growth or dissolution of the solid phase even when the temperature inadvertently changes or is in error by a small amount. The only commonly used diffusion source for III-V compounds and their alloys is Zn. This is diffused from the vapor for which the source may be elemental Zn, or in the case of GaAs, it may be ZnAs2 or the 3-phase mixture GaAs + Zn2As3 + ZnAs2, where the function of the compound sources is to maintain the stoichiometry of the compound. The problem with this diffusion source is that the surface concentration is fixed at 1020 cm3 or higher where stoichiometry is not maintained in the compound. Thus for making a structure like the Transverse Junction Stripe Double Heterostructure Laser l, it is necessary to do a shallow diffusion at high concentration followed by a drive-in diffusion from this limited source to obtain the required Zn concentration of N 1019 cm3 in the active layer of the laser. The drive-in diffusion also necessitates a very long process at a high temperature for reasons which are not fully understood, but which appear to be associated with the fact that fast diffusion takes place when there is a source of both the diffusing species and vacancies, while diffusion is slow when one of these sources is removed. The only way to obtain lower surface concentrations of Zn is to work in a region of the phase diagram where a liquid phase is present
2. This is generally avoided because such a liquid on the surface of a wa...