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Monolithic Planar LED Arrays by One Diffusion Step

IP.com Disclosure Number: IPCOM000075780D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Blum, JM: AUTHOR [+2]

Abstract

For some LED materials, it is difficult to provide isolation diffusions because extremely thick layers of the LED material must be grown in order to obtain good quality material, and deep diffusions into these materials will cause degradation of the material. To overcome this problem and to provide good optical isolation, AlGaAs LED arrays are provided by a single diffusion step.

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Monolithic Planar LED Arrays by One Diffusion Step

For some LED materials, it is difficult to provide isolation diffusions because extremely thick layers of the LED material must be grown in order to obtain good quality material, and deep diffusions into these materials will cause degradation of the material. To overcome this problem and to provide good optical isolation, AlGaAs LED arrays are provided by a single diffusion step.

A shallow epilayer of N type AlGaAs (about 10 microns) is grown on a semi- insulating or P- type GaAs substrate. An oxide diffusion mask is then deposited on the epilayer. The oxide mask is etched to provide windows into which diffusion will take place. An extra deposition of oxide mask is made in those areas in which the diodes are to be formed. During the diffusion step, the isolation diffusion will be a deep diffusion while the device diffusion will be a shallow diffusion, since the dopants are impeded by the thin layer of oxide mask in the region over which the device is to be formed. Consequently, a single diffusion step yields two junction depths.

This type of isolation is suitable in material that is sufficiently close to the substrate for the diffusion to reach it using practical diffusion processes. In AlGaAs layers, it is possible to get good LED material close to the substrate, because the lattice constants of the material and the substrate closely match one another.

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