Browse Prior Art Database

LED Array Having Backside Contact for Improved Reliability

IP.com Disclosure Number: IPCOM000081177D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Audet, LA: AUTHOR [+5]

Abstract

Backside contacts on light-emitting diode (LED) arrays reduce fabrication operations and increase device reliability. Internal light reflections or crosstalk between adjacent diodes in the light-emitting array may also be reduced, by the formation of an Ntype metal contact on the cathode or back surface of the array. A controlled sintering heat cycle insures the formation of an Nr layer along the back surface of the array. Laser scribing of the array into individual chips also contributes to minimizing reflected light, either from the edges of the chip or from the bottom surface.

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LED Array Having Backside Contact for Improved Reliability

Backside contacts on light-emitting diode (LED) arrays reduce fabrication operations and increase device reliability. Internal light reflections or crosstalk between adjacent diodes in the light-emitting array may also be reduced, by the formation of an Ntype metal contact on the cathode or back surface of the array. A controlled sintering heat cycle insures the formation of an Nr layer along the back surface of the array. Laser scribing of the array into individual chips also contributes to minimizing reflected light, either from the edges of the chip or from the bottom surface.

A semiconductor substrate 10, typical gallium arsenide and the like and of N type receives a plurality of P type diffusions 12 to form light-emitting junction areas. Suitable contacts, not shown, are connected to the P region. A common cathode, backside contact 14 is also attached to the element 10. The cathode connection 14 may be formed by electro-chemical, chemical or by vacuum evaporation process techniques. The contact metallurgy is either gold-rich, Au/Sn alloy; a silver-rich, Ag/Sn alloy; a gold-rich, Au/Ni/Sn alloy; or a silver-rich, Ag/Ni/Sn alloy. Small amounts of S, Se and/or Te may be added to these alloys to insure the Nnature of the contact. A sintering cycle of from five to thirty minutes at temperatures between 400 degrees to 500 degrees C ensures adequate time for establishing an Nlayer 16 on the back surface of...