Fabrication and characterization of opto-electronic devices based on p-type thin-film semiconductors

In order to achieve large-area photodetection over a few cm2 with higher sensitivity, higher opto-electronic transfer efficiency and lower cost, two p-type thin-film semiconductors, CIGS and CuO, are investigated in this thesis to realize high-performing large-area opto-electronic devices based on the investigations of novel fabrication processes, device designs, characterization and simulation results. CIGS photodiodes are optimized firstly by reducing the CIGS thickness below 1 um, introducing industry-compatible flexible steel substrates, alkali doping and multiple buffer layers (CdS and Cd-free In2S3). Dual-mode photodetection of CIGS photodiodes is fully characterized for the first time both in the photovoltaic and photoconductive modes. In addition, a corrected photoconductive gain mechanism is firstly investigated to accurately explain the operation mechanisms of CIGS photodiodes. As a more sustainable semiconductor material than CIGS, full fabrication and characterization of large-area CuO thin films and related devices with excellent performances require further investigation. Targeting the best-performing p-type CuO with a bandgap around 1.5 to 1.7 eV, a carrier concentration around 10e15 cm-3, an absorption coefficient over 10e5 cm-1, and a maximum carrier mobility, magnetron sputtering is introduced as a reliable technique in the large-area fabrication. To investigate the interfacial properties of CuO with metal and dielectric, the Au/CuO transmission line model (TLM) structures and a CuO metal-oxide-semiconductor (MOS) capacitor are studied. Finally, CuO TFTs with HfO2 gate dielectric are fabricated, characterized, and analyzed on soda lime glass.