Electron Subband Structure and Mobility Trends in P-n
Delta-Doped Quantum Wells in Si
We present the electronic spectrum of a n-type deltadoped quantum well in Si coupled to a p-type delta-doped barrier within the envelope function effective mass approximation. We applied the Thomas-Fermi approximation to derive an analytical expression for the confining potential, and thus, we obtain the electronic structure in a simple manner. We analyzed the electron subband structure varying the distance between the doping planes (l) as well as the impurity density in them (n2D, p2D). We also study the mobility trends through an empirical formula that is based on the electron levels, the electron wave functions and the Fermi level. We find a monotonic decrease in the mobility as the p-type barrier moves away from the n-type well, and optimum parameters, l = 70A and n2D = 5 × 1012 cm-2 and p2D = 5×1013 cm-2, for maximum mobility.