Investigation of the electronic structures of (GaAs) n(AlAs) n short period superlattices by photoluminescence spectroscopy under hydrostatic pressure

Abstract

The photoluminescence of (GaAs) n (AlAs) n short-period superlattices (SLs) with different period lengths ( n=4-17) is studied under hydrostatic pressure in the range of 0–50 kbar at both 300 and 77 K. The dependence of the energy separation between the conduction band Γ-like and X-like levels on the SL periodicity is obtained independent of which level is higher. The type I-type II transition is observed at atmospheric pressure and at both 300 and 77 K in a (GaAs) 11(AlAs) 11 SL. It is found that the pressure coefficient of X-like states decreases with decreasing period length of the SL, changing from -2.2 meV kbar for (GaAs) 17(AlAs) 17 to -1.2 meV kbar . for (GaAs) 4(AlAs) 4. The Γ-X mixing potential V mix obtained from the investigation of the pressure dependence of luminescence intensities at 77 K is 4, 14, 7, 1.4 meV for n=6, 8, 11, 17 samples, respectively. These results demonstrate that the state mixing due to the zone folding effect is quite small though the mixing potential increases slightly with the decrease of the period length of the SL.