Blue, Green, and Amber InGaN/GaN Light-Emitting Diodes on Semipolar {11-22} GaN Bulk Substrates

Abstract

We demonstrate the fabrication of blue, green, and amber InGaN/GaN light-emitting diodes (LEDs) on semipolar {11-22} bulk GaN substrates. The {11-22}GaN substrates used in this study are produced by cutting out from a c-oriented GaN bulk crystal grown by hydride vapor epitaxy. The LEDs have a dimension of 320 ×320 µm2 and are packed in an epoxide resin. The output power and external quantum efficiency (EQE) at a driving current of 20 mA are 1.76 mW and 3.0%, respectively, for the blue LED, 1.91 mW and 4.1% for the green LED, and 0.54 mW and 1.3% for the amber LED. The maximum output powers obtained with a maximum current of 200 mA are 19.0 mW (blue), 13.4 mW (green), and 1.9 mW (amber), while the maximum EQEs are 4.0% at 140 mA (blue), 4.9% at 0.2 mA (green), and 1.6% at 1 mA (amber). It is confirmed that the emission light is polarized along the [1-100] direction, reflecting the low crystal symmetry of the {11-22} plane.

A method used to overcome polarization effects in semi-polar structures of nitride light-emitting diodes emitting green radiation

“…However, taking into account aggregate results of the above analysis, we have decided to choose the (1122) InGaN/GaN LEDs. Efficient long-wavelength emission of these devices has been also reported many times (see, e.g., [23][24][25][26][27]) and their structures seem to have currently more perspective advantages as green emitters [28] among reported orientations to date. In particular, expected highpower green (516 nm) emission has been reported by Sato et al [29] from the InGaN/GaN multi-quantum-well LED manufactured on the (1122) GaN substrate.…”

“…For lower inclination angles ϑ , i.e. for semi-polar orientations, the overlapping depends on a distance of ϑ from its value (about 34 • ) corresponding to [20,21,23,26,27,29,31] the same polarizations in both the quantum well and the barrier (Fig. 6).…”

Geometrical Characteristics and Surface Polarity of Inclined Crystallographic Planes of the Wurtzite and Zincblende Structures

“…The characteristic geometrical properties of the {100} surface are the surface terminated by a single atomic species 6,22 and two dangling bonds per atom on the surface. The same properties are indeed shared with 11 " 22 È É , but not any other wurtzite semipolar planes, as already seen in Fig.…”

“…3-9 Especially, 11 " 22 À Á has attracted vast attention due to its strong ability to incorporate In, aiming for green-light emitters. 6,7 Ueda et al (the group led by Kawakami at Kyoto University) have been growing exclusively on the 11 " 22 À Á GaN substrates. 10 Stimulated emission in the green spectral region was recently achieved.…”

Exciton localization in semipolar (112¯2) InGaN multiple quantum wells

“…In contrast, high efficiency green and yellow semipolar (11 22) InGaN LEDs grown on low threading dislocation density (TDD $ 5 Â 10 6 cm À2 ) high-cost (11 22) GaN bulk substrates have previously been demonstrated. 10,11 By means of time-resolved photoluminescence measurements (TR-PL), it has been experimentally reported that mplane InGaN 4 and (11 22) InGaN [12][13][14] QWs have shorter recombination lifetimes compared to polar QWs. However, it should be noted that those samples show recombination dynamics identical to those observed in polar QWs.…”