Electrical properties of amorphous semiconductor selenium and its alloys. II. Heterojunction multilayers

For pt.I see ibid., vol.2, p.809 (1987). Multilayer amorphous-selenium-based photoreceptor devices were prepared by thermal evaporation in a vacuum at 10-6 Torr and their electrical properties were studied. Xerographic time of flight (XTOF) and conventional time of flight (TOF) were employed to determine the drift mobilities of the charge carriers in the various layers. The measurements were carried out for various composition over a wide range of applied fields. The dopants used were tellurium (to 20 wt.%), arsenic (to 0.5 wt.%) and chlorine (to 60 wt. p.p.m.). Applied fields varied from approximately=5*103 V cm-1 to approximately=105 V cm-1. The data show that the effects of doping and applied field are in general similar to those in the monolayers which illustrates the validity of interpretation of the transient current signals. Novel double layer structures were also prepared to investigate the effect of interface macroscopic mechanical barrier between the layers. Some data are also presented on inverted double and triple layers which are of scientific interest.