Transport Properties Of The Pressure-Induced Amorphous Semiconductor State Of Al32ge68

The temperature dependences of the dc conductivity and thermopower of the bulk amorphous alloy Al32Ge68 were investigated at 6-420 K and at 80-370 K, respectively. The samples were prepared by solid-state amorphization of a quenched crystalline high-pressure phase while heating from 77 to 400 K at ambient pressure. Amorphous Al32Ge68 was found to be a p-type semiconductor with an unusual combination of transport properties. The behaviour of the properties was described semi-quantitatively in terms of a modified Mott-Davis model assuming that the Fermi level lies inside the valence band tail.