Strong carrier confinement in ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ quantum dots grown by molecular beam epitaxy

We report photoluminescence and time-resolved photoluminescence experiments on ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ quantum dots grown by plasma-assisted molecular beam epitaxy. We show photoluminescence from single quantum dots, giving an unambiguous proof of the quantum dot nature of luminescence. In addition, we show that both the photoluminescence intensity and the carrier recombination time remain constant up to $200\mathrm{K}$, reflecting the strong confinement of the carriers inside the quantum dots. We find monoexponential photoluminescence decay times as short as $340\mathrm{ps}$, explained by the lack of the quantum confined Stark effect in our structures.

Figure 1

Time-integrated PL spectrum of the QD emission at $300\mathrm{K}$. The left inset shows a Z-contrast STEM image of an ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ QD. Dotted lines are a guide for the eye. The right inset shows an AFM height image (the greyscale range is 3 nm) of the uncapped version of the ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ QD sample.

Figure 2

The $\mu \text{−}\mathrm{PL}$ spectra from masked QD sample at $4\mathrm{K}$ through a 470 and a $170\mathrm{nm}$ aperture.

Figure 3

Arrhenius plot of the integrated PL intensity of both ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}$ QDs and QW. Solid lines are a guide for the eye.

Figure 4

Spectral dependence of the PL decay time. The time-integrated PL spectrum is represented by a solid line.

Figure 5

(a) Time-resolved PL decay trace for several temperatures. (b) Temperature dependence of the PL decay time.

Figure 6

Time-resolved PL decay trace for several excitation powers.