Al_xGa_1−xN‐Based Quantum Wells Fabricated on Macrosteps Effectively Suppressing Nonradiative Recombination

Abstract

AlxGa1−xN‐based quantum wells (QWs) are fabricated on AlN with macrosteps, which are formed by using vicinal sapphire and AlN (0001) substrates. The QWs on macrosteps (MS‐QWs) show photoluminescence lifetimes of nearly 2 ns at an emission wavelength of 242 nm at room temperature (RT). This is the longest lifetime so far reported for AlxGa1−xN‐based QWs emitting below 270 nm, indicating the suppression of nonradiative recombination, the dominant recombination process at RT. Compared with planar QWs without macrosteps, the emission internal quantum efficiency estimated by photoluminescence spectroscopy is improved approximately by two orders of magnitude under a weak excitation condition. Consequently, AlxGa1−xN‐based MS‐QWs are promising structures for highly efficient ultraviolet emitters.

Efficient Deep Ultraviolet Emission from Self-Organized AlGaN Quantum Wire Array Grown On Ultrathin Step-bunched AlN Templates

“…Generally, the emission intensity of the long-wavelength peak is much lower than that of the short-wavelength peak, meaning that the long-wavelength peak plays a supplementary role in total luminescence. 39 Contrary to previous reports, the relative emission intensity is reversed in this work. The emission intensity of the long-wavelength peak (277 nm) is much higher than that of the short-wavelength peak (267 nm) even at RT.…”

Detailed analysis of Ga-rich current pathways created in an n-Al0.7Ga0.3N layer grown on an AlN template with dense macrosteps

“…AlGaN-based DUV-LEDs fabricated on an AlN template with dense macrosteps using sapphire substrates with high miscut angles such as 1.0°have been reported to have a higher internal quantum efficiency (IQE) than those on flat AlN templates. [13][14][15][16][17][18] The IQE is considered to be boosted by localized carrier injection through Ga-rich zones, which function as current pathways in an n-AlGaN cladding layer. 19) The carrier localization centers created along the edges of multiple quantum wells (QWs) with high IQE, which are combined with current pathways, may dominate the IQE of the device.…”

Singularity structures for sub-250 nm emissions from AlGaN-based semiconductors

“…AlN layers grown on vicinal (0001) substrates often show wavy surfaces, which are composed of bunched macrosteps and atomically flat terraces. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] Growing AlGaN QWs on such surfaces lowers the Al composition and widens the well widths on the bunched steps. 43,44,[48][49][50][51][52][53][54][55] Similarly, compositional fluctuations have also been confirmed in AlGaN films grown on AlN with bunched steps.…”

“…[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] Growing AlGaN QWs on such surfaces lowers the Al composition and widens the well widths on the bunched steps. 43,44,[48][49][50][51][52][53][54][55] Similarly, compositional fluctuations have also been confirmed in AlGaN films grown on AlN with bunched steps. 40,46) Because wider well widths and lower Al compositions in QWs at bunched steps create potential minima, the optical transition energies of QWs on macrosteps (MS-QWs) are lower than those on adjacent planar terraces.…”