Charge transport in the normal state of electron- or hole-doped YBa2Cu3O7-x

By using a field-effect transistor configuration, we have demonstrated that It is possible to dope electrons or holes into an initially underdoped YBa 2Cu3O7-x film at room temperature. The results of systematic measurements o f the dual-type transconductance indicate comparable field-effect mobilitie s for electrons and heres. We propose a model based on band bending and loc alized electronic states within the band gap of the Mott insulator to expla in the dual-type charge transport.