New Applications for CDTE/CDS Heterojunctions: the Prospects of the Thin-Film JFET




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Junction Field Effect Transistors (JFETs) based on II-VI polycrystalline materials are expected to be faster than metal-insulator-semiconductor field-effect transistors (MISFETs) that use the same materials. JFET operation is not based on MIS capacitor theory of operation where generated traps at the oxide-polycrystalline material interface are known to adversely affect the performance of MIS transistors. Pulsed Laser Deposition (PLD) is a physical deposition technique that can transfer precise chemical stoichiometry of the targets onto the substrates. PLD has been demonstrated as an appropriate deposition method for JFET fabrication based in ZnO films. The control of the doping concentration and low leakage currents in PN junction are prerequisites for JFET fabrication. In this dissertation, CdTe/CdS diodes demonstrated low leakage current devices - on the order of nA. Also, CdTe and ZnTe have been doped with Cu, decreasing the resistivity. However, only a Cu doped ZnTe deposited by co-deposition method by PLD modulated the resistivity from 10⁶ to 10² Ω·cm. Simulation results showed that the leakage current values and the doping concentration achieves by PLD are suitable values for JFET fabrication. Masks were designed to fabricate JFETs using a photolithographic process flow. JFETs were fabricated using a Cu:ZnTe(p+)/CdTe(p)/CdS(n+) structure. However, the fabricated JFETs did not show proper behavior because the channel resistivity was not modulated by the gate voltage. Some experiments are proposed as possible solutions to fabricate a fully functioning thin-film JFET with Cu:ZnTe(p+)/CdTe(p)/CdS(n+) structure deposited by PLD.



Cadmium telluride, Cadmium sulfide, Heterojunctions, Junction transistors, Field-effect transistors, Thin films, Diodes


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