Effect of asymmetric doping on electron transport mobility in In0.53Ga0.47As/ In0.52Al0.48As wide quantum well FET structure

We analyze the electron mobility μ due to asymmetric doping in In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As wide quantum well field effect transistor (QWFET) structure. By restricting the doping concentrations nd 1 and nd 2 in the barriers, ( nd 1 + nd 2 ) = 4 × 10 18 cm −3 , we vary μ vs. nd 1 . An increase in well width w (>170 Å) introduces double-subband occupancy (D-SO) symmetrically about nd 1 = 2 × 10 18 cm −3 such that for w ≥ 180 Å, D-SO occurs throughout the range of nd 1 . We consider alloy disorder (al-), ionized impurity (imp-) and interface roughness (ir-) scatterings. Under D-SO, the subband mobilities μ 0/1 imp/al/ir and μ 1 imp/al/ir vary nonlinearly with nd 1 through intra- and inter-subband scattering rates. The variation of μ with w depends upon the doping combinations and SO. The change of μ with nd 1 also shows interesting trends for different w through intersubband effects , exhibiting a cusp-like μ around nd 1 = 2 × 10 18 cm −3 for w = 380 Å. Our analysis of nonlinear electron mobility can help to examine the inter-subband effects on device characteristics of QWFET systems.