Avalanche injection in CdS films

The phenomenon of current-controlled negative resistance has been previously at forward bias in Ge diodes [1]-[3], various p-i-n diodes [4], and recently also in thin oxide films [5], [6] of NB, Ta and Ti. There is a considerable fundamental and technical interest in this phenomenon; and, a number of physical mechanisms [1]-[3], [5]-[8] proposed to explain the negative resistance have been the subject of discussion. It is the purpose of this communication to report the observation of this phenomenon in this filsm of CdS and further, discuss the relevant evidence in support of physical process of avalanche ionization considered to be responsible for the observed effect.