500-nm Optical Gain Anisotropy of Semipolar (11\bar22) InGaN Quantum Wells

Abstract

We studied the effect of carrier population on light emission polarization of green InGaN quantum wells (QWs) on the semipolar ð11 22Þ plane. The 3 nm thick QWs emitting light at about 540 nm at low pumping power have electrical field (E) component E k ½ 1 123 stronger than that E k ½1 100. However, we found that increasing the pumping power changed the sign of the polarization ratio. Using the varied stripe length (VSL) method, we measured the optical gain for light propagating k½ 1 123 direction to be 2 times that of light propagating k½1 100 direction. We explain this behavior by inhomogeneous QW state filling.

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.…”

Evidence of lattice tilt and slip in m-plane InGaN/GaN heterostructure

“…V C 2011 American Institute of Physics. Light-emitting and laser diodes grown on wurtzite GaN with nonpolar 1-5 and semipolar [6][7][8][9][10][11] orientations attract attention because of their lower or absent quantum-confined Stark effect in InGaN quantum wells. [12][13][14] A large (11%) lattice mismatch between GaN and InN causes a significant misfit strain as In composition increases in the heteroepitaxial InGaN layer grown on the GaN substrate.…”

True-green (11-22) plane optically pumped laser with cleaved m-plane facets

“…Other advantages of growth on semipolar planes are reduced quantum confined Stark Effect and polarization anisotropy allowing higher optical gain if the stripe is positioned in a preferred direction. [5][6][7] Recently, LDs grown on (20-21) semipolar plane substrates have shown very promising characteristics 3 but their laser cavities are oriented toward the c-direction, which requires cleaving along high order planes. Obtaining high facet reflectivity with good yield is therefore challenging.…”

“…10, while in our experimental structures, it is enhanced by QW composition spatial fluctuations. 7 As a result, aligning the stripe in m-direction increases gain only near transparency. The operation near transparency is realized in our low threshold green OPLs using an undoped structure with low internal optical loss and high reflection (HR) mirror coatings.…”