Valence band states and polarized optical emission from nonpolar and semipolar III–nitride quantum well optoelectronic devices

Abstract

Nonpolar and semipolar III–nitride quantum wells (QWs) and devices have been extensively studied due to their unique valence band (VB) structure and polarized optical emission. Unlike conventional c-plane oriented III–nitride QWs, the low crystal symmetry and unbalanced biaxial stress in nonpolar and semipolar QWs separates the topmost VBs and gives rise to polarized optical emission. Since the first experimental reports on nonpolar devices, research on this topic has progressed very rapidly and has covered nonpolar m-plane and a-plane QWs and devices as well as semipolar , , and QWs and devices. Issues such as strain, plane inclination angle (with respect to the c-plane), indium composition, temperature, and their impact on QW VB structure and device performance have been extensively studied. In this paper we review the physical background and theoretical analysis of the VB states and polarized optical emission of nonpolar and semipolar structures and discuss their potential impacts on optoelectronic devices. Experimental results for nonpolar and semipolar light-emitting diodes and laser diodes will be covered along with additional discussions on the potential applications and challenges related to their unique physical properties.

A study of the optical and polarisation properties of InGaN/GaN multiple quantum wells grown on a-plane and m-plane GaN substrates

“…[14,15] From a theoretical point of view [16] the change of nonpolar plane should make no difference to the polarisation properties of InGaN/GaN QWs. At the moment this behaviour is not understood.…”

Optical properties of highly polarized InGaN light-emitting diodes modified by plasmonic metallic grating

“…The photon emission inside QW is represented by dipoles with different orientations. For those nonpolar and semipolar InGaN QW LEDs, the emissions are not totally polarized along one direction, which is widely discussed in various literatures [10][11][12][13][14][15] by involving the polarization ratio ( ) / ( )…”

“…To circumvent these negative effects, novel nonpolar and semipolar InGaN LEDs have been proposed and demonstrated with reduced QCSE, higher efficiency, and smaller carrier lifetime [6,7]. Other advantageous features including high efficiency, improved performance in green spectral region, and polarized emission, were also reported for nonpolar and semipolar devices [8][9][10][11][12][13][14][15][16][17][18].…”

“…Since the emission frequency of the InGaN/GaN QW is located near the resonance frequency of SPs at the metal/GaN interface, exploiting the plasmonic effect to enhance spontaneous emission is promising to further reduce the carrier lifetime for InGaN LEDs [20][21][22][23]. On the other hand, it has been reported that nonpolar and semipolar InGaN/GaN QWs have highly-polarized emission due to the separation of light hole (LH) band, heavy hole (HH) band and crystalfield split-off hole (CH) band [10][11][12][13][14][15][16][17][18]. Compared with conventional c-plane devices, optical properties such as F P and carrier lifetime can be further enhanced by the polarized emissions from nonpolar and semipolar InGaN QW LEDs, because the coupling efficiency from the spontaneous emission to the surface plasmon modes is dependent on the transverse magnetic (TM) component of the light [24,25].…”

Polar properties of a hexagonally bonded GaN sheet under biaxial compression

“…Group III nitride semiconductors with a Wurtzite structure, such as GaN and its derivatives, have attracted much attention because of their excellent optical and electrical properties for applications as optical and high-frequency electronic devices because of their high carrier mobility and wide direct band gap. [9][10][11][12][13] For example, InGaN-based quantum well structures have enabled high-performance light-emitting diodes and laser diodes covering from violet to green wavelength regions. 14) Furthermore, high-density two-dimensional electron gas at the interfaces in AlGaN/GaN heterostructures allows them to be promising materials for high-electron mobility transistors with high voltage and low resistivity.…”