Wavelength-stable cyan and green light emitting diodes on nonpolar m-plane GaN bulk substrates

Abstract

We report the development of 480 nm cyan and 520 nm green light emitting diodes (LEDs) with a highly stable emission wavelength. The shift is less than 3 nm when the drive current density is changed from 0.1 to 38 A/cm2. LEDs have been obtained in GaInN-based homoepitaxy on nonpolar m-plane GaN bulk substrates. For increasing emission wavelength we find a large number of additional dislocations generated within the quantum wells (2×108 to ∼1010 cm2) and a decrease in the electroluminescence efficiency. This suggests that the strain induced generation of defects plays a significant role in the performance limitations.

Polar dependence of impurity incorporation and yellow luminescence in GaN films grown by metal-organic chemical vapor deposition

“…The problem can be avoided by growing GaN in nonpolar orientations, in which the polar c-axis is at 901 to the growth direction; alternatively, the electric field can also be reduced by growing in semipolar orientations, in which the c-axis is at an acute angle to the growth plane [2]. So recently there have been considerable interests in the growth of nonpolar and semipolar gallium nitride based on epitaxial films, heterostructures and devices [3][4][5][6][7][8]. The polar properties of GaN make the behaviors of the different polar directions distinct, especially when there is impurity incorporated.…”

Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods

“…Growing InGaN multiple quantum wells (MQWs) with sufficient In% to emit light above 520 nm has been difficult due to the crystallographic defects formed, better known as the "green gap". 6 As InGaN grown on GaN increases in thickness there is a huge stress caused by the lattice mismatch. 7 The main stress relieving mechanisms possible for epitaxially grown InGaN on planar layers is through dislocation formation [8][9] which are known to have a significant impact on the internal quantum efficiency.…”

Rare-Earth-Free Direct-Emitting Light-Emitting Diodes for Solid-State Lighting

“…The extremely limited amount of total available substrate area amounting to far less than a single 2-in c-plane wafer on sapphire attests to a very limited opportunity to properly dial in dopant flows and orientation-specific growth parameters. Also, in these cases of nonpolar m-and a-axis growth, a significant light output power drop with longer wavelength always correlated with a large increase in the density of line defects as seen in cross-sectional TEM [22]. These defects specifically start in the quantum wells themselves, suggesting the need for the design of better interfaces between GaN barriers and GaInN quantum well layers.…”

“…At the same time, growing any heterostructures along a direction perpendicular to the polar c-axis avoids all polarization effects along the growth direction [20]. In this way, nonpolar a-axis [21] and m-axis [22] grown heterostructures can be achieved without any dislocation defects discernible in cross-sectional transmission electron microscopy (TEM) (equivalent to densities < 10 6 cm −2 ).…”