DIFFERENT PATHS TO TUNABILITY IN III-V QUANTUM DOTS

Tunability in the concentration and average dimensions of self-farming semiconductor quantum dots (QDs) has been attained. Three of the appr oaches examined here are: variations with temperature, group V partial pressure and with substrate miscut angle. Thermally activated group I II adatom mobilities result in larger diameters and lower concentratio ns with increasing deposition temperatures. These variations are prese nted for InGaAs/CaAs and AlInAs/AlGaAs, where striking differences wer e seen. Tunability in the InGaAs/GaAs QD concentration was also obtain ed in metalorganic chemical vapor deposition by varying the arsine flo w. The latter gave widely varying concentrations and similar sizes. Su bstrate orientation was found to also be a key factor in island nuclea tion: Changes in vicinal orientation near (100) can be used to exploit the preferential step edge nucleation at mono and multi-atomic steps, so varying miscut angle (theta(m)) can be used to change island densi ties and sizes. Anisotropies in island nucleation producing n-dot stri ngs aligned with multiatomic step edges are observed for theta(m)great er than or equal to 0.75 degrees and up to 2 degrees. Quantum mechanic al coupling from such island strings result in non-Gaussian shapes in the inhomogeneously broadened photoluminescence peaks. The effects of some of the other morphological differences presented here on the lumi nescence emission from QD ground states is discussed for InGaAs/GaAs Q Ds. (C) 1998 American Institute of Physics.