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Elimination of Dislocations in Heterojunction Lasers

IP.com Disclosure Number: IPCOM000080701D
Original Publication Date: 1974-Jan-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 17K

Publishing Venue

IBM

Related People

Blakeslee, AE: AUTHOR [+3]

Abstract

A method has been devised for eliminating dislocations in heterojunction lasers so as to improve laser lifetimes.

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Elimination of Dislocations in Heterojunction Lasers

A method has been devised for eliminating dislocations in heterojunction lasers so as to improve laser lifetimes.

It is believed that the degradation of a GaAs PN junction laser is due to the movement, under forward bias of the laser, of fast-diffusing impurities such as copper into the junction region. Copper, as well as other metals, precipitate upon dislocations, thus providing impurity traps that lead to laser degradation.

The devised method makes use of the slight lattice mismatch that exists at the interface between GaAs and GaAlAs (two materials forming a junction of a heterojunction laser), in order to eliminate the formation of dislocations during growth of the GaAs and GaAlAs crystals.

Climb and glide are two mechanisms by which dislocations in crystals can move. It is desirable to transform those dislocations that thread the crystal into configurations called "misfit" dislocations. Threading configurations are deleterious, because they move upwards through the crystal as the latter is grown. A misfit dislocation can move sidewise of a grown crystal and disappear at the sides of the crystal. By transforming threading dislocations into misfit dislocations during the growth of a substrate, a point is reached when the upper levels of the substrate are free of dislocations, permitting the subsequent epitaxial growth of dislocation-free PN junctions.

The use of a combination of climb and glide, permits pre...