Uniaxial-strain effects on n = 1 free-exciton and free-carrier lines in GaAs

Abstract

Photoluminescence at liquid-helium temperature from free excitons in GaAs has been studied for zero strain and for [100] stresses from 33 to 500 kg cm-2. At zero strain (group Td) there are three exchange-split exciton lines Λ5 (J = 1, allowed), and Λ3 and Λ4 (J = 2, forbidden, and at lower energy than J = 1). The Λ5 line is strain split by [100] stress χ (group D2d) into a higher-energy line X2 of σ polarization (⊥ stress) and a lower- energy line X1a of π polarization (∥ stress). The Λ4 lines gives, with this strain, an allowed, lower-energy line X1b of σ polarization. The exchange splitting E between Λ5 and Λ4 is 0.37 ± 0.04 meV. Theory predicts relative strengths X1a:X1b:X2 of π:0:σ for E ≪ strain splitting Δ hv, changing to π:σ/2:σ/2 for Δ hv ≪ E, and our data are consistent. The deformation potential coefficients for the Λ5 exciton states are a = -9.76 ± 0.03 eV and b = -1.52 ± 0.06 eV. The dependence of EG on χ has been determined and found to be more rapid than that for X1a. The value for G(1) thus derived is 4.4 ± 0.04 meV and for EG we find 1.51996 eV ± 0.04 meV for one sample.