Decomposition Resilience of GaN Nanowires, Crested and Surficially Passivated by AlN

Abstract

The rapidly increasing interest in nanowires (NWs) of GaN and associated III-Nitrides for (opto-)­electronic applications demands immediate address of the technological challenges associated with NW-based device processing. Toward this end, we demonstrate in this work an approach to suppress the thermal decomposition of GaN NWs, which also serves to passivate the surface states. Both of these effects are known to be significant challenges in the development of GaN-NW-based devices. The approach entails AlN capping of the as-grown GaN NWs, in the same molecular beam epitaxy growth step. We show that the epitaxial AlN crest that grows on the top facet of the NW arrests thermal decomposition, while the AlN shell on the sidewalls (together with the crest) protects the NW surface from the generation of oxygen-induced surface states. This simple approach can be used for the development of GaN-NW-based devices.

Scaling Nanowire-Supported GaN Quantum Dots to the Sub-10 nm Limit, Yielding Complete Suppression of the Giant Built-in Potential

“…The length and diameter of the AlN-capped GaN NWs of sample I are the same as those of the as-grown NWs of this sample (550 and 56 nm, respectively). This confirms that the AlN-cap protects the underlying GaN NWs from thermal decomposition, as demonstrated in our earlier work …”

“…The distinct strategy developed for realization of the GaN NWQDs by MBE is schematically shown in Figure . Thermal decomposition of GaN NWs at high temperatures (either during growth or during postgrowth thermal annealing) is now well-established. , In a previous report, we have shown that this decomposition can be completely suppressed by cresting the as-grown GaN NWs with a thin AlN cap layer . Combining this capability with controlled decomposition of GaN NWs is the crucial enabling step of the NWQD formation technique, demonstrated here.…”

“…26,27 In a previous report, we have shown that this decomposition can be completely suppressed by cresting the as-grown GaN NWs with a thin AlN cap layer. 28 Combining this capability with controlled decomposition of GaN NWs is the crucial enabling step of the NWQD formation technique, demonstrated here. Accordingly, GaN NWs of length ∼550 nm and diameter ∼58 nm were first grown and crested with a ∼3 nm AlN cap (Figure 1a) at 880 °C.…”

“…This confirms that the AlN-cap protects the underlying GaN NWs from thermal decomposition, as demonstrated in our earlier work. 28 Figure 3a−f shows the TEM images of NWQD samples I, II, and III, together with samples consisting of quantum disks (samples IV and V). The whole candle-like structure is shown in Figure 3a.…”

Carrier-Induced Defect Saturation in Green InGaN LEDs: A Potential Phenomenon to Enhance Efficiency at Higher Wavelength Regime

“…III-Nitride materials for optoelectronic applications have gained unprecedented interest around the globe due to their bandgap tuning ability, spanning from deep UV to near-infrared region. − InGaN-based green light emitting diodes (LEDs) and laser diodes (LDs) with high efficiency are of particular importance due to their vast relevance in display applications, undersea submarine communication, pico-projectors, medical surgery, etc. − Despite relentless efforts by various research groups, poor efficiency remains a major issue to look into with indium incorporation crossing 20% (peak emission wavelength λ p ≥ 500 nm). − This imminent setback comes to play mainly because of the non-radiative defects, owing to high lattice mismatch and adverse growth conditions to incorporate high indium composition. − Defects in the active region play an important role in determining the performance of these optical devices by opening a non-radiative channel for injected carriers in the QWs. − Here, we demonstrate that all the defect states in the active region do not necessarily participate in the non-radiative recombination process. Instead, they can be saturated with carriers at high injection.…”