Epitaxy of germanium using germane in the presence of tetramethylgermanium

Epitaxial germanium (Ge) growth from germane (GeH4) has been investigated in the presence of organometallic tetramethylgermanium (TMGe) in the temperature range of 675–825 °C. Under the growth conditions employed, the growth of Ge is essentially mass-transport limited with an optimum growth temperature of 725 °C. The presence of TMGe does not increase Ge growth rates but lowers background-carrier concentrations in undoped n-type Ge layers. This reduction in background-carrier concentration is more pronounced at higher growth temperatures. In addition, the presence of TMGe yields more abrupt p+-n junctions, possibly suggesting the formation of more ‘‘defect-free’’ epitaxial growth of Ge from GeH4 and reduced boron diffusion into n-Ge layers.