Homoepitaxial growth of germanium for photovoltaic and thermophotovoltaic applications

In the present work homoepitaxial Ge layers were deposited by means of metal organic vapor phase epitaxy (MOVPE) on Ge using iso-butyl germane (iBuGe) as a metal organic precursor. Layers of different thicknesses were grown by varying the deposition temperature between 550 and 700°C on n- and p-type Ge substrates. The films were found to be intrinsically p-type with high carrier concentration, but using AsH3 it was possible to achieve n-type doping. TEM and X-ray diffraction were used to assess the good crystallographic quality of the layers. By depositing a p-type layer onto an n-type Ge substrate or, vice versa, an n-type layer on a p-type Ge substrate is was possible to realize p/n (or n/p) junctions. Mesa structures were realized in order to perform electrical characterizations of the junctions.