Methods for Fabricating III-Nitride Tunnel Junction Devices

Brief Description

Methods of physical vapor deposition for III-nitride tunnel junction devices.

Background

Current commercially-available III-Nitride light-emitting diodes (LEDs) and edge-emitting laser diodes (EELDs) use an active region in a biased p-n junction to allow for electron and hole injection. However, since p-type gallium nitride (p-GaN) is difficult to contact electrically and has low hole concentration and mobility, p-GaN cannot be used as a current spreading layer and traditional p-contacts will add significant voltage to devices. Despite these inherent problems, all commercial light emitting devices utilize a p-contact and a material other than p-GaN for current spreading, typically transparent conducting oxides (TCO).

A tunnel junction is a diode comprised of a very highly doped (n+/p+) interface that allows for electrons to tunnel between the valence band conduction band. Although in principle a highly doped Esaki-type homojunction diode should provide the lowest-loss tunnel junction, there have been a number of difficulties achieving high quality tunnel junctions in the GaN material system.

Description

Researchers at the University of California, Santa Barbara have satisfied the need for improving the performance of III-nitride devices by overcoming the limitations currently in the field. Improvements include alternative methods for creating tunnel junction devices, including physical vapor deposition (e.g., sputter deposition) and MOCVD regrowth deposition, and III-Nitride tunnel junction improvement through reduction of the magnesium memory effect. Self-emissive III-V micro LED-based displays using low resistance tunnel junctions leveraging these improvements have been fabricated.

Advantages

• Eliminates the need for a TCO or silver mirror
• Easy wide scale adoption of sputter deposition tools
• Reduction of excess magnesium in the fabrication of III-nitride junctions
• Fabrication of III-nitride tunnel junction devices using MOCVD for growth

Applications

• LEDs
• Tunnel Junctions
• III-nitride devices

Patent Status