Porous layers on compensated GaAs:Cr

Porous multi-layered structures on GaAs:Cr (001) were formed by anodic etching in HF acid based electrolyte. The top layer with a thickness of 0.5–1.5 μm consists mainly of As- and Ga-oxides. As–O crystallites oriented along 110]-axes were observed. Below the top layer, a porous layer of 2–10 μm thickness is formed with micro-pores of up to 2 μm in diameter. The structure and chemical composition of porous GaAs:Cr was studied by SEM, AFM and photoemission microspectroscopy. The porous GaAs:Cr samples were characterized by spectroscopic ellipsometry and modulation spectroscopy techniques. The optical response of the complex sample was analysed in terms of the pseudodielectric function.