Analysis of morphological, optical and thermal properties of porous p-type indium phosphide p-InP(100) prepared by the vapor etching method

In this paper we report for the first time, the effect of halogenic acids (HCl and HF) on the morphological, optical and thermal properties of porous p-InP layers (p-InP-Ls). The samples were elaborated by a vapor phase etching (VE) method with two halogenic acids (1M HF and 1M HCl). The recording of the porous surfaces' morphology was carried out by Scanning Electron Microscopy (SEM). The porous p-InP-Ls formed using 1M HCl steam was found to have a micro-porous structure in which the pores were distributed on the p-InP(100) substrate. The UV-Visible spectrum revealed that the porous p-InP-Ls formed by 1M HCl steam displayed a greater absorbance capacity in the visible range than the other layer which is formed using 1M HF steam. In addition, it was found that the band gap energy (E-g) of porous p-InP-Ls formed by 1M HCl steam was greater (1.254 eV) than the unetched p-InP substrate (1.228 eV), which was attributed to the quantum size effect. FTIR spectrum showed the presence of peaks related to P-Cl bonds. The thermal conductivity and thermal diffusivity of the porous p-InP-Ls were determined by the photo-thermal deflection technique, which studies the variation of the photothermal signal with the square root of the modulation frequency. The result showed that the vapor of halogenated acids (especially HCl steam) clearly affected the thermal properties.