The Dynamics of High-Field Propagating Domains in Bulk Semiconductors

In the past several years, it was found that several bulk semiconductors showed voltage-controlled differential negative resistance over a certain range of applied electric field. The cause of this negative resistance is vastly different from one material to another. For example, it is attributable to field dependent trapping effect in golddoped germanium, to phonon-electron interaction in CdS and to inter-valley scattering mechanism in GaAs, InP, CdTe and ZnSe. Regardless of the origin, however, the voltage-controlled differential negative resistance effect nucleates a high field domain in the bulk.1 Once it is nucleated, the domain travels toward the anode with al2235 2236 THE BELL SYSTEM TECHNICAL JOURNAL, DECEMBER 1907 most constant velocity; e.g., 107 cm/sec for GaAs and 105 cm/sec for CdS.2 As the domain is absorbed into the anode, another domain is nucleated in the bulk and the whole process repeats again. Although the detailed mechanism of the negative resistance is still a subject of intense discussion, the high-field domain itself appears to have a great significance in future electronics. The objective of this paper is to clarify the dynamics of high-field propagating domains in bulk semiconductors. Since the high field domain in GaAs is presently best understood, we shall mostly concentrate on it. However, similar discussions must be possible for the high field domains in other materials as well.