Large GaAs island growth by low density droplet epitaxy
- Large GaAs island growth by low density droplet epitaxy
- 이은혜; 송진동; 배민환; 한일기; 장수경; 이정일
- Issue Date
- Quantum Dot 2012
- Large GaAs islands (~120 nm height, ~400 nm width, fig (a)) were grown on Al0.30GaAs/GaAs by droplet epitaxy (DE) method. Since a large size of semiconductor quantum dots (QDs) could increase the oscillation strength, the formation of the large semiconductor QDs is one of crucial issues .
The DE is a growth method that group 3 and 5 materials are injected separately.  This growth method is different from a stranski-krastanow (S-K) method, which uses lattice mismatch between two materials, in terms of the growth mechanism. Since metal droplets are formed in advance before an introduction of the group 5, it is critical to investigate a formation of the group 3 metal droplets. As a matter of fact, a density of the islands after an injection of the group 5 could be predicted from a density result of the group 3 metal droplets.
In this research, large Gallium (Ga) droplets were formed on a 50 nm-thick Al0.30GaAs/GaAs (100) substrate. The formation temperature of the Ga droplets was changed, 309 ‘C to 345 ‘C, at a fixed condition of the Ga growth rate (0.0625 ML/s) and the Ga coverage (10 ML). Ga droplets with a 4 ML to 60 ML-Ga coverage were also grown, fixed at 0.0625 ML/s and 333 ‘C of the formation temperature. Figure (b) shows the trend of the density and average width measured from scanning electron microscopy (SEM) images of the Ga droplets as a function of the Ga coverage. This figure indicates that an average width of the Ga droplet depends on the Ga coverage. Meanwhile, its effect on the density is negligible. In addition, an effect of a Ga growth rate on the size and density of Ga droplet will be covered.
The large Ga droplets with ~ 360 nm in width, ~ 60 nm in height were finally grown. After As4 introduction, the GaAs islands were covered with a 300nm-thick Al0.30GaAs. The optical properties of the large GaAs islands could be verified after crystallization by annealing.
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