Characteristic features of acoustoelectric generation and spectrum formation in single-crystal indium antimonide

Certain features of the formation of voltage-current characteristics (VCCs) and the spectrum of the acoustoelectric generation of acoustic and electromagnetic oscillations in indium antimonide crystals are discussed. Experiments were carried out in an ac drift field under synchronism conditions, i.e., when the field half-period is equal to the traveling time of acoustic waves along the crystal between reflecting end faces, as well as in a magnetic field in the Corbino disk geometry, when the amplification is provided by the azimuthal component of the electron drift. The characteristic feature of the experiments on acoustoelectric generation in indium antimonide is a relatively slow build-up of fluctuations, which is due to the small value of the electromechanical-coupling constant of this material. The analysis of the VCCs of samples in the oscillating mode and the corresponding phase portraits revealed a completely regular character of these functions, except for the cases when the VCCs under a given voltage are N-shaped, and the transition to the oscillating mode and its failure are caused by a jump of current. The spectrum formation strongly depends on the parameters of the electron system and has a chaotic nature for sufficiently large concentration of electrons; the position of spectral lines in certain cases crucially depends on external conditions such as the sample temperature and small changes in the electric and magnetic fields. It was proved by special experiments on the study of the VCCs as functions of the sample length that this characteristic can be substantially distorted only in sufficiently long crystals. Thus, for the generation of domains, a certain length seems to be necessary, on which a phase correlation of potential wells that correspond to separate fluctuations occurs.