Strong enhancement of light extraction efficiency in GaInAsP 2-D-arranged microcolumns

Abstract

This paper experimentally demonstrates the strong enhancement of light extraction efficiency in two-dimensionally arranged microcolumns. They were designed like a honeycomb photonic crystal and fabricated into GaInAsP-InP wafers by using the inductively coupled plasma etching. For the laterally directed light passing through the microcolumns, peculiar transmission characteristics were observed, which could be explained by the Bragg reflection theory, namely, the photonic bandgap (PBG). The measurement of spontaneous lifetime showed that the internal efficiency in the microcolumns was reduced by the surface recombination at sidewalls. In contrast, the light extraction efficiency evaluated from the measured photoluminescence intensity, and the internal efficiency was more than ten times that for a planar wafer. This was thought to be due to the expanded escape cone of internal light by the low effective refractive index, and also due to the strong diffraction and scattering of laterally directed light, which corresponds to the second-order Bragg condition. Such effects are expected not only in photonic crystals but also in some disordered structures. We expect this structure to allow a high-efficiency light-emitting diode (LED), since electronic elements needed for current injection devices can be added independently of the effects.

Growth of GaAs/AlGaAs hexagonal pillars on GaAs (111)B surfaces by selective-area MOVPE

“…It can be eliminated, however, by fabricating periodic structure on the surface as the coupling to the leaky (radiation) mode is promoted by diffraction or by the photonic bandgap which prohibits lateral propagation. Some experimental demonstrations have already been reported [23][24][25][26]. In the results shown in Fig.3(b), the PL intensity increases as a.…”

Modified spontaneous emission from a two-dimensional photonic bandgap crystal slab

“…5 (right), which shows a large power enhancement for frequencies above the bandgap over those below or within the gap region. Strong enhancement of the extraction efficiency from a hexagonal lattice of semiconductor microcolumns has also been observed by Baba et al 24 but without a corresponding enhancement of the power extraction. For this geometry, there was no measurable change in the spontaneous lifetime.…”

“…4. Since experimental measurements [22][23][24] are typically un- der conditions of constant thickness (d/), the calculations for constant d/a 11,16 cannot be directly compared. The emission rate, extraction and detection efficiencies, and the detection rate are shown in Fig.…”

“…For this geometry, there was no measurable change in the spontaneous lifetime. 24 However, the power extraction in the presence of nonradiative recombination mechanisms depends on both the spontaneous emission rate and the extraction efficiency.…”

Directional emission control and increased light extraction in GaN photonic crystal light emitting diodes

“…Early on, photonic crystals 6 ͑PhCs͒ were studied as a means of controllably extracting guided light in other material systems. [7][8][9][10][11] The added advantage from PhC extraction is that, when designed properly, the emission direction can be tailored, increasing light emission in useful directions and reducing the need for lossy reflectors. However, improvements in PhC GaN LEDs have been limited to factors of ϳ1.5-2 times 12-15 despite much higher increases predicted theoretically.…”