Toshi Sanada

Time-Resolved Cyclotron Resonance Analysis of Electron-Exciton Interaction in Silicon

Through time-resolved analysis, it has been concluded that the linewidth of cyclotron resonance for electrons in pure silicon crystal for a certain short interval of time after strong photo-excitation is primarily determined by interaction with isolated excitons. In combination with the work by Cuthbert, the magnitude of electron-exciton interaction is estimated. It lies between those of electron-neutral donor and electron-neutral acceptor interactions.

Magnetoplasma resonance of exciton drop system in germanium

Abstract Two new absorptions which are believed at least partially connected with magnetoplasma resonance within high density exciton drops are observed below 2.2.K in 35GHz cyclotron resonance at germanium under the configuration that E ∥ 〈100〉 and H ∥ 〈001〉. One of them appears very close to the light hole cyclotron resonance signal and is qualitatively interpreted in terms of a simplified magnetoplasma theory, while the other shoots up near zero magnetic field and remains yet unexplained.

Effects of Positively Charged Acceptor Centers on Cyclotron Resonance in p-Type Silicon

The low temperature line-broadening of the electron cyclotron resonance in boron-doped silicon observed in the past experiment is reinterpreted in the light of new observation with the time-resolving method. The contribution of lifetime broadening once suggested is negated and scattering by A + centers, or positively charged acceptors, is now considered the most dominant source for making the linewidth.

Donor to Acceptor Electron Transfer in Germanium at Low Temperatures

Electron transfer process from neutral donor to neutral acceptor in germanium has been observed at liquid helium temperatures in the form of a slowly decaying photoconductivity tail after the flash of the band-gap light. The decay time constant is governed by the leakage flux of room temperature black body radiations upon the sample. Through analyzing the d.c. conductivity as well as Hall data, microwave cyclotron resonance and far-infrared magneto-absorption, the carrier capture cross sections by neutral impurities are determined as a function of temperature: 8×10 -17 cm -2 for the capture of electrons at neutral acceptors and 5×10 -16 cm -2 for that of holes at neutral donors, at 4.2 K with a dependence of T -2 .

Diffusion of excitons and electron-hole drops in germanium

Abstract Diffusion of excitons and electron-hole drops is investigated in pure germanium, using a time-resolved cyclotron resonance method. The diffusion coefficient of excitons at 4.2 K is obtained to be ≈ 1000 cm2/sec. For electron-hole drops, when excitation is not so high, it is expected to be lower than ≈ 500 cm2/sec at 1.6 K.

New Cyclotron Resonance Absorption Peaks in Germanium under High Excitation

New absorption peaks are observed in time-resolved cyclotron resonance for germanium under a fairly high excitatin. They are associated with proper cyclotron resonance signals in a systematic way. Characteristic behavior of these peaks is described in detail. A tentative interpretation of the phenomenon in terms of the idea “excitonic polaron” is attached.

Magnetoplasma Interference Effect on the Microwave Cyclotron Resonance Lineshape in Highly Excited Germanium –Reinterpretation of “Excitonic Polaron”–

The splitting of the microwave cyclotron resonance absorption line in highly excited pure germanium is reexamined. We have reached the conclusion that it is a kind of resonant magnetoplasma interference effect which causes the line-splitting.

An old story of new cyclotron resonance peaks in highly excited germanium

Some modification is suggested for the interpretation of the emergence of new strange peaks in time-resolved cyclotron resonance of germanium under high excitation. The excitonic polaron model suggested earlier is still kept, but the presence of electron-hole drops as the source of supply of free excitons and carriers has to be called for.

Cyclotron reonance study of diffusion problems in highly excited germanium

Diffusion coefficients of excitons and electron-hole drops in pure germanium are measured. Use is made of 35 GHz time-resolved cyclotron resonance method. The diffusion coefficient of excitons at 4.2 K turns out to be ≈ 1000 cm2/s. For electron-hole drops it is lower than ≈ 500 cm2/s at 1.6 K.

Uniaxial Stress and Temperature Dependent Stability of Electron-Hole Drops in Germanium

The decay process of electron-hole drops in germanium created by an intense photopulse is studied with help of 35 GHz microwave cyclotron resonance monitoring and 119 pm laser plasma absorption. From the microwave experiment the work function for surface evaporation is derived as a function of uniaxial stress at 1.5 K, while from the far-infrared experiment one has been able to obtain the temperature dependence of the work function.