Heating by exciton and biexciton recombination in GaAs/AlGaAs quantum wells

A comprehensive experimental investigation of exciton and biexciton recombination in GaAs/AlGaAs quantum wells is presented. Exciton and biexciton recombination times are found to be 16 and 55 ps, respectively. A method of determining the dynamics of the exciton temperature is developed. It is shown that both exciton and biexciton recombination processes increase the exciton temperature by an amount as high as $\sim 10$ K. These processes impose a new restriction on the possibility of exciton Bose-Einstein condensation and make impossible its achievement in a system of direct excitons in GaAs quantum wells even for resonantly excited exciton gas.

Figure 1

(a) PL spectra, corresponding to the different times after the excitation pulse (symbols) fitted with Lorentzian peaks (lines). The spectra are normalized to the maximum value and vertically shifted. (b) Dynamics of the exciton (full symbols) and biexciton (open symbols) PL intensities. (a), (b) Exciton-resonant excitation ($\mathrm{\Delta }=0$ meV) with $P=0.25$ mW, $T_{\text{latt}}=10$ K.

Figure 2

Exciton-resonant excitation ($\mathrm{\Delta }=0$ meV). (a) Exciton intensity dynamics in linear polarizations parallel (solid lines) and perpendicular (dashed lines) to the excitation polarization for different excitation powers. $T_{\text{latt}}=10$ K. (b) Power dependencies of the fast component decay time for the linearly (squares) and circularly (circles) polarized excitations. $T_{\text{latt}}=10$ K. (c) Temperature dependence of the fast component decay time for linearly polarized excitation with $P=0.013$ mW (different excitation spot position on the sample).

Figure 3

Dynamics of exciton (squares) and biexciton (circles) PL intensities for biexciton-resonant excitation ($\mathrm{\Delta }=-1$ meV) with $P=0.13$ mW. The inset shows power dependencies of the exciton (squares) and biexciton (circles) time-integrated intensities for biexciton-resonant (full symbols) and exciton-resonant (open symbols) excitations. $T_{\text{latt}}=10$ K.

Figure 4

(a) Dynamics of the exciton PL intensities (symbols) at different lattice temperatures for exciton-resonant excitation with $P=0.13$ mW. The lines show the exponential fits. (b) Lattice temperature dependence of the exciton PL decay time (symbols). The line shows the linear fit.

Figure 5

Dynamics of the exciton intensity (a) and internal temperature (b) for excitations with different excess energies $\mathrm{\Delta }$ with respect to the exciton resonance and $P=0.13$ mW. Lines in Fig. 5 show exponential fits. $T_{\text{latt}}=10$ K.

Figure 6

Dynamics of the exciton (solid symbols) and biexciton (open symbols) intensities (a) and the internal temperature (b) for exciton-resonant excitation ($\mathrm{\Delta }=0$) with different powers. Lines in Fig. 6 show biexponential fits. $T_{\text{latt}}=10$ K.