Growth variations and scattering mechanisms in metamorphic In0.75Ga0.25As/In0.75 Al0.25As quantum wells grown by molecular beam epitaxy

Publication date: 1 September 2015
Source:Journal of Crystal Growth, Volume 425
Author(s): Chong Chen , Ian Farrer , Stuart N. Holmes , Francois Sfigakis , Marc P. Fletcher , Harvey E. Beere , David A. Ritchie
Modulation doped metamorphic In0.75Ga0.25As/In0.75Al0.25As quantum wells (QW) were grown on GaAs substrates by molecular beam epitaxy (MBE) with step-graded buffer layers. The electron mobility of the QWs has been improved by varying the MBE growth conditions, including substrate temperature, arsenic over pressure and modulation doping level. By applying a bias voltage to SiO2 insulated gates, the electron density in the QW can be tuned from 1×10¹¹ to 5.3×10¹¹ cm⁻². A peak mobility of 4.3×10⁵ cm²V⁻¹s⁻¹ is obtained at 3.7×10¹¹ cm⁻² at 1.5K before the onset of second subband population. To understand the evolution of mobility, transport data is fitted to a model that takes into account scattering from background impurities, modulation doping, alloy disorder and interface roughness. According to the fits, scattering from background impurities is dominant while that from alloy disorder becomes more significant at high carrier density.