Development of Nonpolar and Semipolar InGaN/GaN Visible Light-Emitting Diodes

Abstract

This article reviews the development of nonpolar and semipolar InGaN/GaN light-emitting diodes (LEDs), emphasizing structures on freestanding bulk GaN. A brief history of LED development on each orientation is provided, followed by a discussion of the most relevant and recent results. The context is related to several current LED issues, such as the realization of high-efficiency white solid-state lighting, potential solutions to the “green gap,” and applications for polarized emitters. The section on nonpolar LEDs highlights high-power violet and blue emitters and considers the effects of indium incorporation and substrate miscut. The section on semipolar GaN reviews the development of LEDs in the violet, blue, green, and yellow regions and highlights the potential of InGaN/GaN LEDs as an alternative technology to AlInGaP for yellow emitters. A brief review of polarization anisotropy also is included for each orientation. Finally, a two source white light system utilizing a nonpolar blue LED and a semipolar yellow LED is presented.

A method used to overcome polarization effects in semi-polar structures of nitride light-emitting diodes emitting green radiation

“…However, it should be remembered that efficiency of semipolar InGaN/GaN QW LEDs drastically decreases at longer wavelengths due to difficulties associated with a growth of InGaN layers of high Indium composition [1]. This growth required relatively low growth temperatures, which often results in a degraded crystal quality [2].…”

“…Wolczanska 219, 90-924 Lodz, Poland e-mail: wlodzimierz.nakwaski@p.lodz.pl attracted a great interest of research centers due to their possible applications in manufacturing visible and even ultraviolet light emitting diodes (LEDs). These materials, however, differ significantly from most of other III-V semiconductors, which leads for example to problems with obtaining efficient nitride sources of green radiation ("green gap" effect) [1][2][3]. Their special properties are connected with their wurtzite crystal structure, distinctly different from the zinc blende structure of most of other III-V semiconductors.…”

“…Recently, however, relatively thick c-oriented GaN substrates have been reported (e.g., [11]). Then proper slicing may be used to produce nonpolar or semipolar native GaN substrates [2,5].…”

“…In nonpolar LEDs, however, an increase in an Indium content results in degraded crystal quality because of required low growth temperatures [2]. Efficiency of some similar semipolar LEDs also decreases for longer wavelengths, but to much less extent.…”

“…They create serious problems especially in highly strained InGaN/GaN QWs with high Indium content designed to emit green radiation [1,2]. However, it is shown in Sect.…”