Cyclotron resonance over a wide temperature range, I. Germanium

Abstract

A systematic investigation of cyclotron resonance in germanium has been carried out at 8·8 mm wavelength throughout the temperature range 2 to 100 °K. Typical expressions for the collision times derived from the line width of the cyclotron resonance in high-purity material are: light-mass hole τ − 1 = 0.24 × 10 11 + 1.85 × 10 8 T 1.5 s − 1 ; heavy-mass hole τ − 1 = 0.15 × 10 11 + 1.85 × 10 8 T 1.5 s − 1 electrons τ − 1 = 0.1 × 10 11 + anomaly + 4 × 10 8 T 1.5 s − 1 Between 20 and 100 °K lattice wave scattering is the dominant relaxation process and the collision times derived from the cyclotron resonance are in good agreement with corresponding mobility values. There is an anomaly in the collision time for electrons at about 20 °K which can be explained in terms of resonant scattering from a deep attractive potential well. The residual scattering at low temperatures for both holes and electrons appears to arise from neutral scattering sites. The cyclotron resonance from holes in germanium is modified by copper and gold impurities. With large impurity concentrations the heavy-mass hole is almost isotropic. This effect may arise from a motional narrowing of the absorption lines. In highest purity p -type germanium an additional absorption line has been observed which arises from a carrier with effective mass 0·27 m e .