Complete orientational access for semipolar GaN devices on sapphire. Issue 1 (16th September 2015)

• Record Type: Journal Article
• Authors: Leung, Benjamin; Wang, Dili; Kuo, Yu‐Sheng; Han, Jung
• Is Part Of: Physica status solidi. Volume 253:Issue 1(2016)
• Page Start: 23
• Page End: 35
• Publication Date: 2015-09-16
• Subjects: light‐emitting diodes -- MOCVD -- semipolar GaN; Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.201552301
• Languages: English
• ISSNs: 0370-1972

Abstract

Abstract : Semipolar ( 20 2 ¯ 1 ) GaN light‐emitting diodes and ( 20 2 ¯ 1 ¯ ) GaN films are demonstrated on sapphire substrates. The processes developed here embody all the required steps in order to produce planar semipolar devices on sapphire substrates with complete control of the crystallographic orientation. Theoretical and experimentally observed aspects of semipolar materials and devices on bulk substrates are reviewed, including device performance and orientation‐dependent material properties. This summary motivates the use of particular semipolar orientations having Miller indices ( hkil ), with l < 0, such as ( 20 2 ¯ 1 ¯ ) and ( 30 3 ¯ 1 ¯ ). These orientations have not, as of yet, been shown to be obtained using sapphire substrates. With the appropriate nitridation and buffer layer growth condition on stripe‐patterned sapphire, high quality single crystal ( 20 2 ¯ 1 ¯ ) GaN films have been achieved. Demonstration of surface planarization, device layer regrowth, and LED operation, performed here on semipolar ( 20 2 ¯ 1 ¯ ) GaN, detail the processes to enable planar semipolar‐based devices on sapphire with these unique orientations. With these advances, the required foundation has been put into place to allow access to the potentially highest performance semipolar planes while using economically feasible, large area sapphire substrates. Processes to produce ( 20 2 ¯ 1 ) LED devices (top left) on GaN films grown on full 2″ sapphire substrates (bottom left) are described in this paper. The achievement of ( 20 2 ¯ 1 ¯ ) GaN paves the way toward achieving full orientational access on sapphire substrates (right). Abstract : Of the infinite varieties of polar, nonpolar and semipolar orientations for GaN, determining which one is the most promising for ultra‐high efficiency light‐emitting diodes has been a continuing exploration. Here, we review the current picture of orientation‐dependent material and device properties, uncovered by the use of bulk GaN substrates. We then show the same flexibility of accessing any orientation can be achieved with large area, cost effective sapphire substrates.