Semi/non-polar nitride quantum wells for high-efficient light emitters

Abstract

We describe the optical properties of semi/non-polar InGaN and AlGaN quantum wells. In semipolar (1122) InGaN QWs, spatially uniform but spectrally broad emissions are observed. This finding is interpreted with consideration of the exciton migration length shortened by the fast radiative recombination lifetime due to the reduced electric field. Non/semipolar AlGaN QWs are also fabricated. In the semipolar (1102) AlGaN QWs, the radiative recombination lifetimes faster than that in the (0001) QW are confirmed experimentally. As a consequence, much stronger emission is achieved from the semipolar AlGaN QWs at room temperature.

Structural and optical properties of (112̅2) InGaN quantum wells compared to (0001) and (112̅0)

“…Hence, while the height of step-bunching is small, the regions with more step edges have a more (112̅ 0) like bond arrangement and hence incorporate less In as discussed in section 3.1 and figure 1. Thus the step-bunching This local variation could also explain the recent findings with scanning near field optical microscopy (SNOM) on (112̅ 2) QW, which found a narrowing of PL FWHM on (112̅ 2) QWs when reducing the SNOM aperture from 30 to 10 nm [52]. For the smaller aperture the sampling may have been limited to terraces, depending on the dimension of the step-bunching.…”

Enhanced Performance of the Non-Polar Ultraviolet Light-Emitting Diodes with Lattice-Matched Quaternary Quantum Barriers

“…Considering the anisotropy of the non-polar material, the strain between the quantum wells and barriers along the (1-100) m-direction and the (0001) c-direction could be respectively defined as: . (5) . (6) where and are the lattice constants of the quantum barriers.…”

“…The low EQE is attributed to the strong quantum-confined Stark effect (QCSE) induced by the spontaneous and piezoelectric polarization along the [0001] c-direction, which could generate strong built-in electric fields up to MV/cm in the active region. In contrast, since there is no spontaneous polarization-induced built-in electric field in the non-polar AlGaN epi-layers, higher light emission efficiency is expected for the non-polar AlGaN-based UV-LEDs than the conventional polar c-plane AlGaN-based UV-LEDs [4,5].…”