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 li ght-emitting diode (TFLED), in which a composition-graded n layer and carbon-increasing p layer respectively replace the constant optical-ga p p-a-SiC:H layer and n-a-SiC:H layer employed in the previously repor ted double graded-gap (DG) TFLED and which contains dopant-graded p-i and i-n junctions, was successfully fabricated tu improve the electrol uminescence (EL) of TFLED. This device had a brightness of 400 cd/m(2) at an injection current density of 600 mA/cm(2) and its EL threshold voltage (V-th) was only 9.0 V. The device EL spectrum showed a peak at 586 nm wavelength and emitted yellowish-orange light. The proposed TF LED had good stability of EL intensity and the EL spectrum during norm al operation. The optimum conditions of rapid thermal annealing (RTA), which improved the ohmic contact between the amorphous layer and exte rnal electrode of the device, were 5 min at 300 degrees C in a 250 Tor r H-2 ambient.