Double Graded-Gap Hydrogenated Amorphous Silicon Carbide Thin-Film Light-Emitting Diode with Composition-Graded N Layer and Carbon-Increasing P Layer

An hydrogenated amorphous silicon carbide (a-SiC:H) p-i-n thin-film light-emitting diode (TFLED), in which a composition-graded n layer and carbon-increasing p layer respectively replace the constant optical-gap p-a-SiC:H layer and n-a-SiC:H layer employed in the previously reported double graded-gap (DG) TFLED and which contains dopant-graded p-i and i-n junctions, was successfully fabricated to improve the electroluminescence (EL) of TFLED. This device had a brightness of 400 cd/m² at an injection current density of 600 mA/cm² and its EL threshold voltage (V _th) was only 9.9 V. The device EL spectrum showed a peak at 586 nm wavelength and emitted yellowish-orange light. The proposed TFLED had good stability of EL intensity and the EL spectrum during normal operation. The optimum conditions of rapid thermal annealing (RTA), which improved the ohmic contact between the amorphous layer and external electrode of the device, were 5 min at 300°C in a 250 Torr H₂ ambient.