Annealing effects on the two-dimensional electron gas in strained Si/Si 1− xGe x modulation-doped single quantum wells

Abstract

Shubnikov–de Haas (S–dH) and Van der Pauw–Hall effect measurements on as-grown and annealed strained Si/Si 1− x Ge x modulation-doped single quantum wells grown by the gas source molecular beam epitaxy have been performed in order to investigate the thermal annealing effects. The observation of the S–dH oscillations and the quantum Hall effect at 0.4 K clearly demonstrated the occupation of the Si quantum well by a two-dimensional electron gas (2DEG). S–dH measurements at 5 K on as-grown Si/Si 1− x Ge x single quantum wells showed that the mobility and the carrier concentration of the 2DEG were 20,000 cm 2 V −1 s −1 and 1.4×10 12 cm −2, respectively, the corresponding values of the Si/Si 1− x Ge x single quantum wells annealed at 700°C for 7 h were 13,900 cm 2 V −1 s −1 and 1.6×10 12 cm −2, respectively. These results indicate that the electron mobility and the carrier density of the 2DEG in the Si/Si 0.7Ge 0.3 single quantum well are affected significantly by the annealing treatment.