Spectroscopic studies of random telegraph noise in small $\mathrm{InP}$ quantum dots in ${\mathrm{Ga}}_x{\mathrm{In}}_{1-x}\mathrm{P}$

We have observed and investigated random telegraph noise in the photoluminescence $\left(\mathrm{PL}\right)$ from small $\mathrm{InP}$ quantum dots $\left(\mathrm{QDs}\right)$ in $\mathrm{GaInP}$. Very few of the $\mathrm{QDs}$ exhibit switching between two states, which have similar total intensities, but distinctly different spectra. Usually, one of the states dominates at low excitation power and the other at high excitation power. The switching occurs on the time scale of one second and is stable with respect to annealing at room temperature, but the $\mathrm{QDs}$ can be permanently settled in one of the states by strong illumination. Measurements on $\mathrm{QDs}$ in a semitransparent Schottky diode show that the $\mathrm{QDs}$ can be reversibly forced into one of the states by applying a reverse bias of the order of $1\mathrm{V}$. This switching behavior is different than what has been previously observed because there is no change in the total $\mathrm{PL}$ intensity and, at the same time, both states cannot be explained as simply being shifted by an electric field, but show distinctly different emission spectra.

Figure 1

(Color online) Spectra from two switching $\mathrm{QDs}$ at different excitation powers. States 1 and 2 are shown in blue (light gray) and red (dark gray), respectively. The $\mathrm{QD}$ shown in (b) was permanently quenched to state 1 by strong illumination.

Figure 2

(Color online) Occurrence of states 1 and 2 plateaus of different length (symbols) and the corresponding exponential fits (lines), for another switching $\mathrm{QD}$. The inset shows several traces recorded at different excitation powers, where states 1 and 2 are represented by high and low intensity, respectively.

Figure 3

(Color online) Spectra from a switching $\mathrm{QD}$ in a semitransparent Schottky diode recorded at different excitation powers (a) and different biases (b). States 1 and 2 are shown in blue (light gray) and red (dark gray), respectively. The $\mathrm{QD}$ could be reversibly forced into state 2 by applying sufficiently large reverse bias.

Figure 4

(Color online) Spectra from another switching $\mathrm{QD}$ in a semitransparent Schottky diode recorded at different excitation powers (a) and different biases (b). States 1 and 2 are shown in blue (light gray) and red (dark gray), respectively. The $\mathrm{QD}$ could be reversibly forced into state 1 by applying sufficiently large reverse bias. Three subsequent spectra are shown superimposed for biases below $-1\mathrm{V}$ to illustrate the continuous spectral diffusion observed in the $\mathrm{QD}$ luminescence for large reverse biases. The $\mathrm{QD}$ was permanently quenched to state 2 by strong illumination.