Capacitance characterisation of Cu 2 S/CdS heterojunctions

Studies of the capacitance of all sputtered Cu x S/CdS heterojunctions are presented. C-F characteristics are measured in the range 100 Hz to 10 MHz and at temperatures ranging between 220 and 340 K. A deep donor level in the CdS is identified 0.25 eV below the conduction band edge. A relative distribution of interface states is deduced from C-V measurements at forward bias and low frequencies. Two types of heterojunctions are examined: (i) with a low density of interface states and (ii) with a higher density of these. Both types of heterojunction were obtained by controlling the parameters of the sputtering process at the junction formation.