Exciton $g$ factor of type-II $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{As}$ single quantum dots

We investigated the magneto-optical properties of type-II $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{As}$ quantum dots using single-dot spectroscopy. The emission energy from individual dots presents a quadratic diamagnetic shift and a linear Zeeman splitting as a function of magnetic fields up to 10 $T$, as previously observed for type-I systems. We analyzed the in-plane localization of the carriers using the diamagnetic shift results. The values for the exciton $g$ factor obtained for a large number of a $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{As}$ dots are mainly constant, independent of the emission energy, and therefore, of the quantum dot dimensions. The result is attributed to the weak confinement of the holes in type-II $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{As}$ quantum dots.

Figure 1

(a) Height vs radius of the $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{As}$ SAQDs obtained from the AFM image in $1\times 1\mu {\mathrm{m}}^2$. (b) PL spectrum measured at $6\mathrm{K}$. The solid line corresponds to the fitting using two Gaussian bands (dotted lines) and the inset shows a schematic diagram of the type II QD or QW potential profile along the growth direction.

Figure 2

(a) $\mu \text{−}\mathrm{PL}$ spectra of type-II $\mathrm{In}\mathrm{P}∕\mathrm{Ga}\mathrm{As}$ SAQDs for different magnetic fields applied along the growth direction, (b) Zeeman splitting energy vs $B$, and (c) Diamagnetic shift energy vs $B^2$ obtained for three single QDs.

Figure 3

(a) Diamagnetic coefficient ${\alpha }_d$ and (b) exciton $g$ factor $g_x$ (left) and Zeeman splitting for $B=10\mathrm{T}$ (right) vs emission energy for a series of single QDs.