MOVPE growth of homoepitaxial germanium

Abstract

n-Type Ge epitaxial layers were deposited on p-type Ge substrates by means of metal-organic vapour phase epitaxy (MOVPE) at temperatures ranging from 500 to 600 °C using isobutylgermane (iBuGe) as metal-organic precursor and hydrogen as carrier gas. The samples were grown at different iBuGe partial pressure conditions and were characterised by means of atomic force microscopy (AFM), high-resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The layers grown with iBuGe partial pressure of 3.3×10 −6 bar at 550 °C show a good crystallographic structure, flat surface and a good interface with the substrate, while for lower partial pressures a series of pits was evidenced on the layer. The pit density was found to be dependent on the growth rate. n-Ge/p-Ge diodes, obtained with standard photolitographic techniques, show rectification ratios higher than 10 5 and ideality factors in the 1.008–1.010 range.