Cyclotron resonance in high mobility Si: the effect of carrier heating

We investigate the cyclotron resonance (CR) of high mobility photo carriers in high resistivity bulk Si in a standard X-band ESR setup. At 2.5 K and low microwave power very narrow CR lines are seen allowing precise evaluation of the cyclotron masses. In addition, we investigate the effect of electron heating caused by microwave absorption which may be related to the recently discovered magneto-oscillations of the dc conductivity of a 2D electron gas with very high mobility under microwave irradiation. Here, in this experiment we observe also an effect of CR absorption on the 3D dc conductivity. The minimum CR linewidth of 1.5 mT implies an electron mobility exceeding 7E5 cm2/V.s. Fitting data for the line width and amplitude as a function of laser and microwave power and temperature with a model that considers deformation potential scattering, we are able to derive the electron temperature. The latter is a function microwave power and the magnetic field. It becomes maximum directly at CR. We evaluate the dependence of temperature on magnetic field and verify the model by comparing it with the complex shape of the CR spectrum. Electron heating is surprisingly effective. For a lattice temperature of 2 K, the electron temperature reaches 10 K at a microwave power of 10 mW, and the temperature increases by 25 mK at 1 microwatt, in spite of the fact that sample is located in the microwave cavity in the minimum of electric field. (author)