In modern production methods for light-emitting diodes (LEDs), the light-emitting layer sequence is often first grown on a growth substrate, subsequently applied to a new carrier, and then the growth substrate is detached. This method has on the one hand the advantage that growth substrates, in particular growth substrates suitable for the production of nitride compound semiconductors, which are comparatively expensive, can be reused. Such a device is known for example from U.S. patent application Ser. No. 10/377,363. This method, referred to as thin-film technology, also has the advantage that the detachment of the original substrate allows the disadvantages of the latter, such as for example a low electrical conductivity and increased absorption of the radiation generated or detected by the optoelectronic device, to be avoided. As a result, the efficiency of LEDs, in particular the brightness, can be increased.
A further technology for the production of highly efficient LEDs is so-called flip-chip technology. Such a device is disclosed for example in U.S. Pat. No. 6,514,782. Described therein is a radiation-emitting semiconductor chip which is connected to a carrier substrate both by the n contact and by the p contact by means of a direct soldered connection.
Both in thin-film technology and in flip-chip technology, it is advantageous to form the contact between the semiconductor chip and the carrier substrate as a reflecting contact. In this way, penetration of the radiation generated or detected by an optoelectronic device into the contact is avoided and consequently the absorption losses are reduced.
Such a reflecting electrical contact is disclosed for example in U.S. Pat. No. 6,194,743. In this document, a silver layer is specified as a suitable ohmic contact for a p-type GaN semiconductor. However, mention is also made of the low adhesive strength and corrosion resistance of silver layers on nitride compound semiconductors.
USPTO Backgrounds
USPTO Backgrounds