Influence of technological parameters on the behavior of the hole effective mass in SiGe structures

We present a study of some features of a two-dimensional hole gas confined in a Si/Si1-xGex/Si/SiO2 structure when the external applied gate bias is v aried. From the framework of the effective-mass theory, and applying the se miaxial approximation to separate the 6x6 Luttinger Hamiltonian into two 3x 3 matrices, we calculated the hole density profile and the band structure. This enabled us to evaluate, in an iterative process, the Poisson and Schro dinger equations until convergence was achieved, obtaining the above-mentio ned results for a discretional angle in the k(x)-k(y) plane, and thus inclu ding the warping. We identified in this way the influence of the different technological parameters which determine the behavior of the device, in par ticular, through the determination of a unique effective mass. We conclude that the utility of this kind of device lies more in the possibility of mod ifying the band structure due to the strain introduced than in the fact of being able to confine carriers in the Si1-xGex channel. Accurate calculatio n of the band structure is, therefore, needed and although simpler simulati ons can qualitatively model some features of the device, a complete study a s described in this article must be carried out in order to obtain better i nsight into the physics of the system. (C) 2000 American Institute of Physi cs. [S0021-8979(00)01815-6].