Novel pore shape and self-organization effects in n-GaP(111)

n-type GaP(111) has been porosified in HCl, H₂SO₄, HBr, NaBr, and alkaline NaBr in the dark. The pore morphology strongly depends on the electrochemical conditions and on the chemical nature of anions in the electrolyte. Independent of the pH-value of bromide-containing solutions, layers of triangular pores with a defined cross-section were growing under an irregular pore nucleation layer. Optimized conditions led to a regular structure of equally sized triangular pores with a side length of (98 ± 5) nm. The pore walls are determined by (110)-crystal planes of GaP. In other electrolytes such as HCl or H₂SO₄ it was not possible to form triangular pores during the electrochemical etching process.