We report on the technology and growth optimization of GaAs/InAs core/shell nanowires. The GaAs nanowire cores were grown selectively by metal organic vapor phase epitaxy (SA-MOVPE) on SiO2masked GaAs 
templates. These were structured by a complete thermal nanoimprint lithography process, which is presented in detail. The influence of the subsequent InAs shell growth temperature on the shell morphology and crystal structure was investigated by scanning and transmission electron microscopy in order to obtain the desired homogeneous and uniform InAs overgrowth. At the optimal growth temperature, the InAs shell adopted the morphology and crystal structure of the underlying GaAs core and was perfectly uniform.
Source:IOPscience
We identify the entire growth parameter space and rate-limiting mechanisms in non-catalytic InAs nanowires (NWs) grown by molecular beam epitaxy. Surprisingly huge growth temperature ranges are found with maximum temperatures close to ~600 °C upon dramatic increase of V/III ratio, exceeding by far the typical growth temperature range for catalyst-assisted InAs NWs. Based on quantitative in situ line-of-sight quadrupole mass spectrometry, we determine the rate-limiting factors in high-temperature InAs NW growth by directly monitoring the critical desorption and thermal decomposition processes of InAs NWs. Both under dynamic (growth) and static (no growth, ultra-high vacuum) conditions the (111)-oriented InAs NWs evidence excellent thermal stability at elevated temperatures even under negligible supersaturation. The rate-limiting factor for InAs NW growth is hence dominated by In desorption from the substrate surface. Closer investigation of the group-III and group-V flux dependences on growth rate reveals two apparent growth regimes, an As-rich and an In-rich regime defined by the effective As/In flux ratio, and maximum achievable growth rates of > 6 µm h−1. The unique features of high-T growth and excellent thermal stability provide the opportunity for operation of InAs-based NW materials under caustic environment and further allow access to temperature regimes suitable for alloying non-catalytic InAs NWs with GaAs.
Source:IOPscience
We report the first demonstration of electroluminescence at 1.3 µm from InAs/GaAs quantum dots (QDs) monolithically grown on a Ge/Si substrate by metal organic chemical vapor deposition (MOCVD). High-density coalescence-free InAs/Sb:GaAs QDs emitting at 1.3 µm were obtained on a GaAs/Ge/Si wafer. The post-growth annealing of the GaAs buffer layer shows a significant improvement in the room-temperature (RT) photoluminescence (PL) intensity of QDs grown on a GaAs/Ge/Si wafer, comparable to those QDs grown on a reference GaAs substrate. Together, these results are promising for the realization of a QD laser on a Si substrate by MOCVD for silicon photonics application.
Source:IOPscience
