ELECTRONIC-STRUCTURE AND OPTICAL BEHAVIOR OF SELF-ASSEMBLED INAS QUANTUM DOTS

Using both electrical and optical techniques, ground state energy leve ls and excited states of carriers in self-assembled InAs quantum dots are described, and the first observations of mid-infrared photoconduct ivity in these structures are presented. Electrical measurements inclu ding ac conductance and Hall techniques have been used to determine th ermal trapping of carriers, and yield strong binding for holes, less b inding for electrons, and an exciton energy that is consistent with ph otoluminescence (PL) measurements. Further PL experiments have probed the effect of changing the InAs dot size, and using embedding material of different composition. Several of these structures also demonstrat e strong electron binding. In devices where the InAs dots have been gr own in an Al0.3Ga0.7As matrix and surrounded by AlAs barriers, normal incidence photoconductivity has been observed at a range of wavelength s in the mid-infrared and attributed to single carrier transitions out of the dots. This mid-infrared optical response is investigated for s everal different dot structures and compared to photoluminescence data from the same samples. (C) 1997 American Vacuum Society.