Conditions of coexistence of Tamm and Shockley states in a superlattice with a perturbed surface

摘要: Conditions of electron surface-state existence are studied by means the transfer matrix method in a semi-infinite superlattice with alloy concentration changing either abruptly (square potential) or gradually (sinusoidal potential). A small surface perturbation is introduced into model modifying shape potential well. The effect this on Shockley (S) states studied, special attention paid to threshold which destroys an existing S state shifting it from gap band; for Tamm (T) states, we search minimum value inducing T appear. results obtained show coexistence and within precisely specified range parameter values. theory applied investigate Al x Ga 1 - As superlattice.