M-Plane GaN/InAlN Multiple Quantum Wells in Core–Shell Wire Structure for UV Emission

Abstract

We report on the epitaxial growth of high-quality core−shell nonpolar m-plane GaN/InAlN multiple quantum wells (MQWs) on the sidewall facets of c-oriented hexagonal GaN wires. Pseudomorphic growth without generation of threading dislocations has been established for planar GaN/InAlN (In = 15%) MQWs grown on m-GaN substrates, although m-plane InAlN epilayers cannot be grown perfectly lattice-matched to GaN along the two in-plane directions. Calculations based on elasticity theory indicate that the significant amount of strain oriented along the c-axis is the likely factor favoring the formation of cracks along this direction. For the core−shell wire geometry, such cracks are not observed, leading to high structural quality MQWs. A significant UV emission centered around 3.7 eV at room temperature with a strong polarization perpendicular to the wire axis is observed for those core−shell wires, which is consistent with k•p method calculations, proving the absence of quantum confined Stark effect on nonpolar m-plane surfaces. These excellent optical features reported in the UV spectral range are attributed to the defect-free nature of the GaN/InAlN MQWs, thereby opening promising opportunities for the realization of UV light emitters.

Three-dimensional nanoscale study of Al segregation and quantum dot formation in GaAs/AlGaAs core-shell nanowires

“…27 It has also been observed in other Al-containing hexagonal nanowire structures. [40][41][42] The proxigram defined in the ROI #2 for an Al 21% isosurface is displayed in Fig. 2(e), and shows that these Al segregation planes contain up to 40% Al atomic concentration, with an interface defined over about 2 nm.…”

Направленное излучение нитевидных нанокристаллов GaAs/AlGaAs, легированных бериллием

“…[1]. Для оптоэлектронных приложений структуры типа ННК GaAs в оболочке AlGaAs имеют значительный потенциал в связи с наличием широ-козонного покрывающего слоя, эффективно подавляющего процессы безызлучательной рекомбинации, связанные с высокой плотностью поверхностных состояний в ННК GaAs [2][3][4]. Кроме того, подобная геометрия ННК открывает новые возможности инженерии электрон-ной структуры в радиальных гетероструктурах [5,6].…”

Piezoelectric domains in the AlGaN hexagonal microrods: Effect of crystal orientations

“…1 Engineering the band gap of AlN, GaN and InN finds different applications in the semiconducting industry for their various optoelectronic properties such as photovoltaic, hydrogen storage, light and field emissions. [2][3][4][5][6] Because of the capability to create two-dimensional electron gas at the hetero-junctions, the III-nitrides are used for developing high electron mobility transistors along with the hetero-junction field effect transistors and bipolar transistors. 7 III-nitride based photonic device is also used as ultraviolet (UV)-blue light emissions.…”

“…7 III-nitride based photonic device is also used as ultraviolet (UV)-blue light emissions. 2,8 Among all the III-nitrides, AlGaN is very important because of its applications in high power and high mobility electronic devices. 9,10 The major advantages of the AlGaN alloys are its compatibility of tuning the direct band gap in between the energy ranges from 3.47 to 6.2 eV.…”

“…Thus, AlGaN ternary alloys with different composition plays an important role in UV and deep-UV optoelectronic device applications. 2,11 In addition to their utility as direct band gap material, the III-nitrides exhibit piezoelectricity which establishes their importance, particularly, in different micro-mechanical devices such as micro-actuators, microsensors, ultrasonic motors, micro-pumps, self-powered devices, electro-mechanical sensing, mechanical energy harvesting and other various applications as MEMS based device. [12][13][14][15][16] Piezoelectricity is a phenomenon in which an electric field is generated inside a material subjected to a mechanical strain or vice versa.…”