Impact of structural defects upon electron mobility in InSb quantum wells

Abstract

The detrimental effects of structural defects, micro-twins (MTs) and threading dislocations (TDs), on electron mobility have been investigated for InSb quantum wells (QWs) at room temperature (RT). The constants that are necessary to calculate the electron-mobility limits of these defects were determined by a least-squares-based method that has an advantage of clear representation of the analytical results in a two-dimensional space. Based on a mathematical consideration, a general method of converting electron-mobility limits into percentage impacts upon the total electron mobility was developed. Percentage-mobility-impact analyses showed that, when InSb QWs grown on on-axis (001) GaAs substrates have a TD density of 8.7 × 108 – 3.2 × 109/cm2, 21–14 and 18–45% of electron-mobility degradation are attributed to MTs and TDs, respectively, at RT. The use of 2° off-axis (001) GaAs substrates reduces MT densities in InSb QWs, resulting in a suppression of the MT mobility impact to 3–2% and a complementary slight increase of the TD mobility impact to 22–51% in the same TD density range. This considerable TD mobility limit indicates that it should be possible to improve RT electron mobility in InSb QWs grown on 2° off-axis (001) GaAs substrates, by means of reducing TD density further (< 8.7 × 108/cm2). Although the mobility impacts due to phonons in InSb QW grown on-axis and 2° off-axis (001) GaAs substrates are 54–36 and 67–42%, respectively, phonon scattering is not a single dominant scattering factor: MTs and TDs have also substantial negative impacts upon RT electron mobilities in InSb QWs.