Formation of high-mobility silicon-germanium structures by low-energy plasma enhanced chemical vapor deposition

摘要

A method for making a semiconductor heterostructure in a growth chamber with gas inlet comprises several steps. In a first step, a virtual substrate is formed on a silicon substrate, comprising a graded Si_1-xGe_x layer followed by a Si_1-xGe_x layer with constant concentration of Ge, using a high-density, low-energy plasma enhanced chemical vapor deposition (LEPECVD) process. In this step, the growth rate is maintained above 2 nm/s. the substrate temperature between 400° and 850° C., and the total reactive gas flow at the gas inlet between 5 sccm and 200 sccm. In another step, an active region is formed on said virtual substrate comprising a Ge-channel and a modulation-doped layer using a low-density, low-energy plasma enhanced chemical vapor deposition (LEPECVD) process. In this step, hydrogen (H₂) is introduced into the growth chamber to act as a surfactant, a substrate temperature is maintained between 400° and 500° C. and a dopant gas is introduced in a pulsed manner into the growth chamber to provide for the modulation-doped layer.