Stimulated emission at 474nm from an InGaN laser diode structure grown on a (112¯2) GaN substrate

Abstract

The stimulated emissions from semipolar InGaN laser diode (LD) structures grown on (112¯2) GaN substrates are observed at room temperature under photopumped conditions. The measured emission peaks are in the photon energy range from 2.62eV (474nm)to3.05eV (405nm), and the emission intensity has a threshold behavior with respect to the pumping power. A strong in-plane optical anisotropy is observed between the two perpendicular directions, [1¯1¯23] and [11¯00], due to anisotropic matrix elements, which depend on the crystal orientation; the stimulated emission measured along the [1¯1¯23] direction occurs with a lower threshold pumping power at a lower energy compared to that obtained along the [11¯00] direction. The experimental results and the valence band calculations indicate that the transverse-electric mode with an electric vector along the [11¯00] direction is dominant for gain formation in semipolar and nonpolar InGaN LDs. Compared to c-plane InGaN LDs, semipolar InGaN LDs have comparable or less threshold pumping powers.

Role of strain in polarization switching in semipolar InGaN/GaN quantum wells

“…This affects the splitting of the uppermost valence bands and hence the polarization of the emitted light. A corresponding optical anisotropy has already been observed for both nonpolar 6-8 and semipolar [9][10][11][12][13][14] devices. This raises the question of how to control the polarization of the emitted light, which is not only of scientific interest but also of technical importance for the performance of light-emitting diodes and laser diodes.…”

“…Under high excitation power density the sign of the polarization ratio of InGaN/GaN was found to remain unchanged even at high In content. 13,14 Why the polarization ratio is affected by the excitation power density also remains unclear.…”

Theoretical investigations on anisotropic optical properties in semipolar and nonpolar InGaN quantum wells

“…Some reports have already demonstrated InGaN based light emitting diodes (LEDs) [1,2] and laser diodes (LDs) [3][4][5]. Furthermore, the non c planes have the anisotropic optical properties, which induce polarization for optical transitions, due to low symmetric in-plane alignments of atoms.…”

Optical anisotropy in semipolar (Al,In)GaN laser waveguides

“…One possibility to reduce this effect [3] is to grow the laser diode on a different crystal plane than the commonly used c-plane. Optically pumped LED and laser structures on semipolar [4][5][6] and nonpolar [7,8] planes and even a pulsed laser at 531 nm [9] on the semipolar (2021)-plane have been demonstrated by various groups. Although nonpolar structures have the highest carrier wave function overlaps due to vanishing internal fields, they might not be good candidates for green lasers as there are problems with indium incorporation on nonpolar crystal planes [10].…”