Abstract
Porous superlattices
n-type (100) InP are produced electrochemically on by changing the applied current or potential periodically in 1 M HCl+1 M HNO
3 solutions. The superlattice consists of stack of alternating two layers with various morphologies and porosities. The plan-view morphologies of the top surface of superlattice were almost same, and the pore size was varied in the nano-order range. On the other hand, the cross-sectional morphologies depend strongly on the electrochemical condition. For low applied currents or potentials such as 10 mA or 1.5
V
Ag/AgCl, respectively, porous layers with a facet-like structure were formed. The size of each facet did not change with the etching time, but the number of the facets increased with time. For high currents or potentials such as 50, 100 mA or 3
V
Ag/AgCl, respectively, a tree-like structure with random and/or tangled branches was observed. At a still higher potential of 5
V
Ag/AgCl, the porous layer exhibited fairly regular array of straight pores. Therefore, it is found that the morphology of the porous layer can be highly controlled by the applied current or potential.