Sharp n-type doping profiles in Si/SiGe heterostructures produced by atomic hydrogen etching

Surface segregation of group V dopant during thin film epitaxy of Si/SiGe heterostructures causes severe limitation on the sharpness of n-type doping profiles in pn junctions. Existing techniques for removal of surface segregated arsenic suffer from either high thermal budget or aggressive (ex situ) wet chemical etching. An in situ low temperature method is clearly desirable, particularly for device structures with high Ge content such as resonant tunnelling diodes, in order to minimize diffusion of the matrix elements as well as maintain structural integrity. In situ etching by atomic hydrogen is shown to be ideal for this purpose. The reaction mechanism ensures that this can only be a low temperature process and the method is shown to be highly effective and selective in the removal of surface segregated As. In comparison with other techniques, atomic hydrogen etching is also shown to be less aggressive and has a smaller impact on the surface/interface quality.