Anisotropic strain in (100) ZnSe epilayers grown on lattice mismatched substrates

We show that part of the reflectance difference resonance near the E-0 ener gy of ZnSe is due to the anisotropic in-plane strain in the ZnSe thin films , as films grown on three distinctly different substrates, GaAs, GaP, and Z nS, all show the resonance at the same energy. Such anisotropic strain indu ced resonance is predicted and also observed near the E-1/E-1+Delta(1) ener gies in ZnSe grown on GaAs. The theory also predicts that there should be n o resonance due to strain at, the E-0+Delta(0) energy, which is consistent with experiments. The strain anisotropy is rather independent of the ZnSe l ayer thickness, or whether the film is strain relaxed. For ZnSe films with large lattice mismatch with substrates, the resonance at the E-1/E-1+Delta( 1) energies is absent, very likely due to the poor crystalline quality of t he 20 nm or so surface layer. (C) 2000 American Vacuum Society. [S0734-211X (00)05604-3].