The Hall effect of amorphous and crystalline Asâ‚‚Seâ‚ƒ
Klaffke, Gerald R.
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The dc Hall Effect and electrical conductivity of both crystalline and amorphous As2Se3 have been measured as a function of temperature over the range 300°K to 400°K. The resistivity at 300°K is intrinsic with a value ^1012 ohm-cm in crystalline and 'lO11 ohm-cm in the amorphous form. Hall Effect measurements at these high resistivity levels were facilitated by simple geometric considerations. Thermal, activation energies derived from resistivity and Hall data were approximately equal and correspond to a forbidden energy gap of ^2ev. The Hall constant was negative in all cases showing the predominant charge carriers to be electrons in crystalline As2Se3 and conforming to the n-p sign anomaly with the positive Seebeck coefficient in amorphous As2Se3. The Hall mobility values were -lOO cm2/V-sec in crystalline and 0.2 to 1.0 cm2/V-sec in the amorphous form. The amorphous films were prepared by physical vapor deposition using an electron beam gun in an ion pumped bell jar system. The data appears to support the self-trapped small polaron model rather than the random phase model for disordered systems.