Electron States in Crystals with “nipi‐Superstructure”

Abstract

Abstract A semiconductor with a zigzag‐shaped superstructure potential, caused by the introduction of narrow n‐and p‐doped layers into an intrinsic crystal (“nipi‐crystal”), is considered. For high amplitude and long period of this potential the low lying conduction‐ and the upper valence‐subband states are concentrated around the n‐and p‐layers, respectively. The subbands, as obtained for an idealised mode, neglecting fluctuations of the superstructure potential, are extremely narrow with respect to the direction perpendicular to the layers. Approximative calculations show, that the discrete subband structure should be clearly distinct also if electron‐impurity and electron‐phonon interaction is taken into account. The density of states in crystals with “nipi‐superstructure” is completely different from that in the corresoponding n‐ and p‐doped normal crystals. A non‐equilibrium situation can be quasi‐stable due to the low electron‐hole recombination probality.