Atomic scale characterization of III-V compound optoelectronic materials using cross-sectional scanning tunneling microscopy
Former ICYS-Sengen researcher, Battery Materials Unit, NIMS
III-V compound-based quantum structures have been used as key components in a wide range of optoelectronic devices, including laser diodes, solar cells (SCs), and photo-detectors. Nowadays, state-of-the-art fabrication techniques enable us to achieve highly complicated multiple epitaxial layers with atomic scale precision. However, due to this complexity, the understanding of microscopic details of how they make an effect on the macroscopic device performance is highly preliminary. Macroscopic electrical and optical measurements are not sufficient to confirm the role of design complexity; therefore, a direct measurement of local electronic properties of the quantum structures is required to gain effective design criteria for the optoelectronic devices.
In this talk, first we report on the characterization of a multiple quantum well SC based on GaAs/AlGaAs heterostructures, which is expected to be a potential candidate of intermediate band type SC. We introduce some examples of the atomic scale characterization of the multiple QW using STM, including the atomic arrangement, electronic states, and band profile. Second, we talk about the characterization of dilute GaAs:N that exhibit a variety of optoelectronic properties depending on the density of N impurity. We show that broadening of the N impurity state can be directly visualized using current imaging technique of STM.