COLLECTIVE EXCITATIONS OF ELECTRON DISKS IN LATERALLY PATTERNED SI SIGE MODULATION-DOPED HETEROJUNCTIONS/

Square lattices of isolated electron disks of diameters 0.2-2 mu m wer e obtained by laterally patterning n-type modulation-doped Si/SiGe het erojunctions grown by ultra high vacuum chemical vapor deposition. The disk lattices were fabricated by electron-beam lithography and reacti ve ion etching. The collective excitations in the disks were studied b y microwave magnetotransmission experiments. The resonance dispersion as well as the disk plasma frequencies are theoretically analysed assu ming a nearly parabolic confining potential.