Effective mass and quantum lifetime in a Si/Si0.87Ge0.13/Si two-dimensional hole gas

Abstract

Measurements of Shubnikov de Haas oscillations in the temperature range 0.3–2 K have been used to determine an effective mass of 0.23 m0 in a Si/Si0.87Ge0.13/Si two-dimensional hole gas. This value is in agreement with theoretical predictions and with that obtained from cyclotron resonance measurements. The ratio of the transport time to the quantum lifetime is found to be 0.8. It is concluded that the 4 K hole mobility of 11 000 cm2 V−1 s−1 at a carrier sheet density of 2.2×1011 cm−2 is limited by interface roughness and short-range interface charge scattering.

Hole effective mass in remote doped Si/Si1−xGex quantum wells with 0.05≤x≤0.3

“…3 We have recently observed m* as low as (0.23Ϯ0.02)m e for xϭ0.13 from a detailed analysis of the thermal damping of the Shubnikov-de Haas oscillations. 4 This value is in reasonable agreement with theoretical predictions which range between 0.20m e and 0.25m e . 5,6 In the present work we have determined the hole effective masses for 0.05рxр0.3.…”

“…4,9 We have estimated the interface charge densities in these materials and find that they vary between 2ϫ10 11 cm Ϫ2 for a sample having a 4 K mobility of about 2000 cm Ϫ2 V Ϫ1 s Ϫ1 and 2ϫ10 10 cm Ϫ2 for a mobility of about 18 000 cm 2 V Ϫ1 s…”

“…4,19,13 The coefficient A is a measure of the effects of weak localization and hole-hole interactions. q (T) is then found by putting q Ϸ the elastic scattering time, with ␣ 0 Ϫ1 , which should be a reasonable approximation in the present case where the scattering is of the short range type.…”

Effective mass and band nonparabolicity in remote doped Si/Si0.8Ge0.2 quantum wells

“…13, with n s ϭ2ϫ10 11 cm Ϫ2 . 1,8 There remains some controversy over whether the observed values of m* follow the predicted dependence of strain ͑i.e., Ge content͒. In particular Cheng et al 2 report m* decreasing with increasing x ͑as predicted͒ while Kiehl et al 3 observe no dependence on x which they attribute to compositional nonuniformity.…”

“…To determine m* we follow our previously reported analysis of the temperature dependence of the Shubnikov-de Haas oscillation, 1,8 which accounts for the effects of temperature dependent screening, weak localization, and holehole interactions. The effective mass is used as an adjustable parameter to obtain unity gradient in a plot of ln͓⌬ m (T)/ 0 (T)] versus ͕ln͑ /sinh )Ϫ͓ / c q (T)͔͖ where ⌬ m is the peak value of the longitudinal resistivity extracted using a cubic spline interpolation and rectangular digital filter, 0 is the Boltzmann resistance, ϭ2 2 kT/ប c , c ϭeB/m*, and q is the quantum lifetime.…”