Lateral piezoelectric fields in strained semiconductor heterostructures

Lateral piezoelectric fields exist in almost all strained III-V semiconductor quantum wells. We first discuss the origin of the lateral fields and point out their most important features. Then the controlled creation of lateral piezofields is demonstrated using a series of (110) InAs/GaAs quantum-wire structures. After verification of the structural perfection by high-resolution x-ray diffraction and transmission electron microscopy an optical study unambiguously demonstrates the existence of lateral fields. By increasing the excitation density in photoluminescence experiments we observe pronounced blueshifts of the luminescence lines simultaneously with a clear reduction of the linewidths. Additional evidence comes from time-resolved measurements where a strong dependence of the radiative lifetime on energy is observed. These results are supported by a study of strained structures with other orientations. In (211), (311), and (210) samples we find evidence of lateral piezofields created by interface fluctuations. Our results show that the impact of lateral piezoelectric fields has to be taken into account in any fundamental analysis of strained III-V semiconductor heterostructures. Furthermore, lateral piezoelectric fields represent a different concept to achieve artificial materials with strong optical nonlinearities.