Optical properties of GaN nanowires grown on chemical vapor deposited-graphene

Abstract

Optical properties of GaN nanowires grown on chemical vapor deposited graphene transferred on an amorphous support are reported. The growth temperature was optimized to achieve a high nanowire density with a perfect selectivity with respect to a SiO 2 surface. The growth temperature window was found to be rather narrow (815 ± 5) °C. Steady-state and time-resolved photoluminescence from GaN nanowires grown on graphene was compared with the results for GaN nanowires grown on conventional substrates within the same molecular beam epitaxy (MBE)reactor showing a comparable optical quality for different substrates. Growth at temperatures above 820°C led to a strong NW density reduction accompanied with a diameter narrowing. This morphology change leads to a spectral blueshift of the donor bound exciton emission line due to either surface stress or dielectric confinement. Graphene multi-layered microdomains were explored as a way to arrange GaN nanowires in a hollow hexagonal pattern. The nanowires grown on these domains show a luminescence spectral linewidth as low as 0.28 meV (close to the setup resolution limit).

Selective Area Growth of GaN Nanowires on Graphene Nanodots

“…Moreover, the emission at 3.45 eV characteristic of inversion domain boundaries 42 is pronounced in GaN NWs on AlN/Si substrate, but it is not observed on nanopatterned graphene as has been previously reported for graphene domains. 40 We speculate that the formation of inversion domain boundaries is related with the NW nucleation step and that it is less likely to occur when the nucleation is slowed down. We now study in more detail how the number of NWs per graphene dot evolves with the growth time.…”

“…This phenomenon can be associated with the long incubation time of GaN NWs on graphene. 40 Furthermore, the length distribution for R dot = 50 nm does not tend to zero at zero length: this indicates that, after 4 h of growth, the nucleation of new NWs is still possible on these small dots. It is possible that, on graphene dots smaller than a certain critical size, GaN nucleation could become even more difficult, resulting in an incomplete nucleation, shorter effective growth time, and consequently a smaller NW length.…”

“…It has been previously shown that the growth selectivity critically depends on the substrate temperature. 40 Therefore, the growth temperature for all the samples was fixed at the optimized value of 815 °C.…”

“…Also, GaN NWs grown on chemical-vapor deposited (CVD) graphene were shown to have excellent optical quality. 40 In all previous studies, the NW growth was performed on either large areas of graphene or on self-assembled graphene domains. For many device applications, it is important to fabricate regular arrays of NWs at predefined positions.…”

Исследование Фотоотклика Графена, Полученного Методом Химического Осаждения Из Газовой Фазы

“…Экспозиция ФР проводилась на установке лазерной литографии Heidelberg DWL 66FS. После формирования меток совмещения осуществлялся перенос монослойного графена, полученного методом химического осаждения из газовой фазы (метод CVD) через жидкость [43][44][45][46][47][48]. Перенос графена с исходной поверхности медной фольги осуществлялся за счет жидкостного травления меди в растворе персульфата аммония с предварительным нанесением слоя полиметилметакрилата (PMMA) на поверхность графена [49][50][51][52] Для измерения спектров отражения на макромасштабе использована установка измерения фотолюминесценции и оптического отражения Accent RPM Sigma.…”