AVS 51st International Symposium
    Science of Semiconductor White Light Topical Conference Wednesday Sessions
       Session WL+MS-WeA

Invited Paper WL+MS-WeA5
Ohmic Contacts to (Al)GaN Semiconductors for Light Emitters

Wednesday, November 17, 2004, 3:20 pm, Room 304B

Session: Science of Semiconductor White Light II
Presenter: I. Adesida, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
The direct bandgap of GaN-based semiconductors have made them attractive materials for the realization of a wide range of optoelectronic devices. Examples of devices that are either commercially available or have been demonstrated include short wavelength light emitting diodes (LEDs), solar blind detectors, and laser diodes which have applications in white light illumination, bio-chemical agent sensing, solar UV detection, missile detection, flame and heat sensing, ozone monitoring, and remote sensing. Materials growth and device processing are still critical issues in terms of obtaining highly efficient GaN-based optoelectronic devices. The realization of highly reliable, thermally stable, low resistance ohmic contacts to both n-type and p-type GaN-based semiconductors is essential. To date, the formation of contacts to AlGaN with high Al concentration remain a challenge for various reasons. In this paper, we will describe our work on ohmic contact formation on both n- type and p-type AlGaN of various Al concentrations. Results on n-type contact formation using various metallization schemes will be presented. Contact formation to p-type AlGaN using Pd-based metallization schemes will be presented. Issues of thermal stability of these contacts will be discussed. The efficacy of various surface treatment schemes for GaN and AlGaN to improve the ohmic performance of the contacts will be discussed. Comprehensive studies are being performed to compare the effects of various surface treatment schemes which include both plasma and wet processes on the electrical and material characteristics of GaN and AlGaN semiconductors. Further, the mechanism of formation of ohmic contacts in these semiconductors will be discussed.