A plasma process for ultrafast deposition of SiGe graded buffer layers

Low energy plasma enhanced chemical vapor deposition (LEPECVD) has been app lied to the synthesis of Si-modulation doped field effect transistor struct ures, comprising a SiGe relaxed buffer layer and a modulation doped straine d Si channel. A growth rate of at least 5 nm/s for the relaxed SiGe buffer layer is well above that obtainable by any other technique. Due to the low ion energies involved in LEPECVD, ion damage is absent, despite a huge plas ma density. The structural quality of the LEPECVD grown SiGe buffer layers is comparable to that of state-of-the-art material. The electronic properti es of the material were evaluated by growing modulation doped Si quantum we lls on the buffer layers. We obtain a low temperature (2 K) Hall mobility o f mu(H)=2.5x10(4) cm(2)/Vs for the electrons in the Si channel at an electr on sheet density of n(s)=8.6x10(11) cm(-2). (C) 2000 American Institute of Physics. [S0003-6951(00)01104-9].