Man-made Superlattice Crystals

Multiple closely spaced layers of GaAs
1−x
P
x
, which approximate a one-dimensional crystalline superlattice, have been created by periodically pulsing PH
3
into an AsH
3
-PH
3
-Ga-HCl vapor-growth apparatus. The phosphorus mole fraction varies between maximum and minimum values with a period typically less than 200Å. Structures with up to 150 such layers have been produced. The crystal growth process and methods of characterization are discussed briefly.