Figure 3d shows the In composition in InGaN shells as a function of temperature. It shows that the amount of In has a linear relationship with the temperature and

that In is gradually depleted with the increase in temperature. An EDS was used to determine BV-6 the composition in the InGaN shell (Additional file 2: Figure S2). The optical properties of a vertical COHN (with 2-nm-thick InGaN and 2-nm-thick GaN shells) were characterized through excitation by a He-Cd laser (wavelength of 325 nm) and subsequent measurement of the PL. Figure 3e shows the normalized PL spectra of COHN grown at 600°C to 750°C. COHN shows wavelengths ranging from violet to light green. The peak, the center of PL wavelengths, BI 10773 manufacturer shifts to longer wavelengths from 405 to 425 and 475 nm (3.06, 2.92, and 2.61 eV in photon energy) as indium concentration increases [13, 28]–[30]. This indicates that the optical properties of vertical COHNs can be tuned on the basis of the composition of the InGaN shell. LOHNs can also provide improved optical properties of GaN nanowires. For example, LOHN serves the quantum structures in a longitudinal selleck products direction, which enhances the optical properties due to the quantum confinement

effect [13, 31]. The PL and electroluminescence can also be improved by creating an LOHN p-n junction. To explore these potentials, we have fabricated the vertical LOHN, based on vertical GaN nanowires. Figure 4a shows the GaN/InxGa1-xN LOHN. Our study Calpain indicates that the LOHN can be prepared at a lower temperature (for example, 550°C) compared to that for COHN (600°C to 800°C) under the same conditions. This lower temperature may due to the early liquefying of the bi-metal catalysts and the dissolution of the Ga and In precursors at low temperature, prior to the deposition of the shell on the side surface of the nanowires by the VS mechanism. Hence, the vertical LOHN as well as COHN can be fabricated in our system by simply controlling

the processing temperature. The TEM image shows two layers with the metal catalyst. According to our compositional analysis, the bright layer close to the metal catalyst is the 5-nm-thick In0.4Ga0.6N layer and below that is the pure GaN layer. Figure 4 The GaN/In x Ga 1-x N LOHN. (a) TEM images of LOHN nanowires. (b) Micro-PL of the individual LOHN nanowire. Inset of (b) shows the green emission of end of the LOHN nanowires. In the COHN, the growth of the InGaN layer on the GaN nanowires proceeds through the VS mechanism. However, in the LOHN case, the growth of the InGaN layer proceeds through the VLS mechanism via a catalyst. This difference results in a compositional difference in the heterostructures.