Abstract
Highly uniform InGaN-based quantum dots (QDs) grown on a nanopatterned dielectric layer defined by self-assembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN/GaN QDs with density up to 8 × 1010 cm-2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm. The photoluminescence (PL) studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.
Highlights
We present the selective area epitaxy (SAE) of ultra-high density and highly uniform InGaN-based quantum dots (QDs) on the nano-patterned GaN template realized by diblock copolymer lithography
It is to be noted that the use of SAE approach on dielectric nanopatterns defined by diblock copolymer process resulted in the growths of InGaN QDs without wetting layer, which potentially led to the increase in optical matrix element
To confirm the effect of SiNx deposition on the GaN template surface, PL studies were conducted on two additional types of samples shown in Figure 10, as follows: (1) InGaN QDs grown on nanopatterned GaN template, and (2) planar InGaN quantum wells (QWs) with the same thickness for InGaN and GaN grown on the GaN templates that had been treated with SiNx deposition and HF wet etching, i.e., the same process employed to form the dielectric mask for selective QD growth
Summary
Nitride-based semiconductor devices have tremendous applications in solid-state lighting [1,2,3,4,5,6,7,8,9], lasers [10,11,12,13,14], photovoltaic [15,16,17], thermoelectricity [18,19,20], and terahertz photonics [21,22]. The ideal QDs obtained by the SAE approach [52,53,54,55,56,57], in particular realized by employing diblock copolymer lithography [55,56,57], have comparable QD density to that of S-K growth mode, but potentially have better device performance because of the removal of the wetting layer and better carrier confinement [55,56,57].
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