We present a theoretical study of the effects from symmetric modulation of the envelop wave function on quantum transport in square quantum wells (QWs). Within the variational approach we obtain analytic expressions for the carrier distribution and their scattering in symmetric two-side doped square QWs. Roughness-induced scattering are found significantly weaker than those in the asymmetric one-side doped counterpart. Thus, we propose symmetric modulation of the wave function as an efficient method for enhancement of the roughness-limited QW mobility. Our theory is able to well reproduce the recent experimental data about low-temperature transport of electrons and holes in two-side doped square QWs, e.g., the mobility dependence on the channel width, which have not been explained so far.

We show that the ratio between relaxation lifetimes dominated by roughness-related scatterings in heterostructures is a well-defined function of the correlation length. Thus, we propose an efficient method for individual estimation of the two size parameters of interface profiles from transport data. Instead of the normal simultaneous fitting of both parameters to lifetimes, we adopt a two-step procedure of (i) inferring the correlation length from some lifetime ratio and then (ii) fitting the roughness amplitude to some lifetime. Similarly, the ratio of roughness-induced linewidths in intersubband absorption may give such an estimation from optical data.

We presented a theoretical study of the effects from two-side (2S) doing on low-temperature lateral transport in square quantum wells (QWs). Within a variational approach, we obtained analytic expressions for the carrier distribution, screening function, and autocorrelation functions for various scattering mechanisms. We found that the mobility of a 2S-doped square QW is larger than that of the one-side (1S) doped counter part for scattering from both interfaces or from the top interface. However, the former is smaller than the latter for scattering from the bottom (substrate-side) interface. The mobility of a 2S-doped square QW exhibits a well-width evolution slower than the power-of-six law characteristic of the undoped QW. The mobility may be enhanced by 2S doping. We examine the dependence of the enhancement factor on QW parameters for optimization of the structure. This factor may achieve an order of magnitude, which is much larger than that provided by earlier methods. Our theory is able to reproduce recent experimental data on transport in 2S-doped narrow square QWs, e.g., the mobility dependence on well width and the enhancement factor, which have not been explained so far.

We present a theoretical study of the effect from doping of quantum wells (QWs) on enhancement of the mobility limited by one-interface roughness scattering. Within the variational approach, we introduce the enhancement factor defined by the ratio of the overall mobility in symmetric two-side doped square QWs to that in the asymmetric one-side counterpart under the same doping and interface profiles. The enhancement is fixed by the sample parameters such as well width, sheet carrier density, and correlation length. So, we propose two-side doping as an efficient way to upgrade the quality of QWs. The two-interface roughness scattering is also incorporated to make comparison.

We employ the theory of band-bending effects to explain the channel-width dependence of the mobility of a two-dimentional hole gas (2DHG) in narrow square Si/Si1−xGex/Si quantum well at high Ge content. The numerical calculation of scattering mechanisms is shown in comparison with the ones from the previous computations. Our method enables a better quantitative description of recently measured data about the dependence of the 8 K mobility of holes in a Si/Si0.2Ge0.8/Si quantum well on the channel width varying from 25 − 70Å.