Energy relaxation of two-dimensional carriers in strained Ge/Si<inf>0.4</inf>Ge<inf>0.6</inf> and Si/Si<inf>0.7</inf>Ge<inf>0.3</inf> quantum wells: Evidence for two-dimensional acoustic phonons

We performed heating measurements on holes in a strained Ge/Si0.4Ge0.6 quantum well and electrons in a strained Si/Si0.7Ge0.3 quantum well in the temperature range 0.3-5.5 K. While a power law dependence of carrier temperature on current, Te∼Ia, was observed for both samples, the measured values for the current exponent are different: a=0.50 ± 0.02 for the Ge sample and 0.40 ±0.02 for the Si sample. We attribute this exponent difference to the difference in their phonon dimensionality. © 1997 American Institute of Physics.