Features of electron transport in relaxed Si/Si1 - xGex transistor heterostructures with a high doping level

The low-temperature electrical and magnetotransport characteristics of partially relaxed Si/Si1 - xGex heterostructures with an electron conduction channel in an elastically strained nanoscale silicon layer are investigated. It is demonstrated that the electron gas in the system exhibits 2D properties. A dependence of the conductivity along layers in the system on the degree of elastic-stress relaxation in it is observed. To understand the observed regularities, the potential and the electron distribution over the structure layers are calculated in detail for samples with different layer strains and doping levels. For the structure with x = 0.25, the parameters of the potential barrier and characteristics of the quantum well formed in the Si layer are estimated. It is established that the characteristics of the potential formed near interfaces strongly depend on the initial parameters of the system, in particular, on the degree of the plastic relaxation of elastic stresses and on the doping level. The formation of a thin tunneling-transparent barrier near the upper interface can lead to the redistribution of electrons between the 2D and 3D conduction channels in the structure, which ensures the spread of the measured transport characteristics of the samples during the measurements. The interlayer tunneling transitions of carriers from the 2D state in the Si transport channel to the 3D state of the Si1 - xGex crystal matrix, which are separated by a tunneling-transparent potential barrier near the heterointerface, were observed for the first time during transport in the direction transverse to the layer plane. © 2014 Pleiades Publishing, Ltd