Semipolar (202¯1) GaN and InGaN quantum wells on sapphire substrates

Abstract

Here, we demonstrate a process to produce planar semipolar (202¯1) GaN templates on sapphire substrates. We obtain (202¯1) oriented GaN by inclined c-plane sidewall growth from etched sapphire, resulting in single crystal material with on-axis x-ray diffraction linewidth below 200 arc sec. The surface, composed of (101¯1) and (101¯0) facets, is planarized by the chemical-mechanical polishing of full 2 in. wafers, with a final surface root mean square roughness of <0.5 nm. We then analyze facet formation and roughening mechanisms on the (202¯1) surface and establish a growth condition in N2 carrier gas to maintain a planar surface for further device layer growth. Finally, the capability of these semipolar (202¯1) GaN templates to produce high quality device structures is verified by the growth and characterization of InGaN/GaN multiple quantum well structures. It is expected that the methods shown here can enable the benefits of using semipolar orientations in a scalable and practical process and can be readily extended to achieve devices on surfaces using any orientation of semipolar GaN on sapphire.

Complete orientational access for semipolar GaN devices on sapphire

“…Of the second type, artificial semipolar planes, devices have only been shown by further thick HVPE growth and polish process to similarly produce quasi‐bulk semipolar GaN substrates . Here, following our previous demonstration of a metal‐organic chemical vapor deposition (MOCVD)‐only single‐step growth process to produce substrates of this type , we demonstrate semipolar () LED devices on sapphire. Finally, of the third type, artificial and with orientation ( hkil ) where l < 0, no devices or even material has been demonstrated.…”

High Quality, Mass‐Producible Semipolar GaN and InGaN Light‐Emitting Diodes Grown on Sapphire

“…However, this blocking/burying effect cannot be applied in other semipolar orientation which has a too large or too small angle with respect to [0001] direction, for instance, (201). Despite the flexibility of OCE in rendering almost arbitrary crystallographic orientations of GaN, the process of OCE still produces SFs albeit with a somewhat lower density . It remains highly desirable to eliminate the SFs and produce SF‐free semipolar or nonpolar GaN films on large‐diameter substrates.…”

Progress in high-luminance LED technology for solid-state lighting

“…If the radiative recombination lifetime could be significantly reduced by improving electron and hole overlap within the quantum well, this would intrinsically reduce the carrier density in each QW, and thus, push out the current density at which Auger recombination becomes a significant loss. Many advances have been accomplished in non‐polar and semi‐polar III‐nitride LEDs , however, more work is required to improve material quality of cost effective and manufacturable solutions. By vertically stacking LEDs with tunnel junctions, the same luminance can be achieved at a lower current density as compared to a typical single junction LED, thereby allowing each LED in the stack to run closer to its peak efficiency.…”