| dc.description.abstract | In a-Si:H emitter heterojunction bipolar transistors (HBT's), a heavily phosphorous-doped n-a-si:H was used as a wide-bandgap emitter material. Since the optical gap of a-Si:H is about 1.8 eV and the bandgap of c-Si is 1.12eV, respectively, so a band-gap discontinuity could be formed between emitter and base. In a HBT the shallower the base junction depth is, the higher the device operation speed, the base resistance, and hence the device VBE, and current gain are. A shallow base junction also decrease the VCE breakdown voltage due to punch-through. Therefore, in this study, the a-Si:H emitter layer and p-type c-Si:H base region were highly doped to obtain sufficient QE , suitable QE/QB, and base resistance which was around 10~60 kΩ. The transition from n-a-Si:H to n-type poly-silicon emitter would be performed by the later used of rapid thermal annealing. The employed base junction depth could be shallow since there was no high temperature process after base junction was formed by using ion implantation. A low-cost , high-speed HBT which was compatible with conventional BJT process was expected.
Also, the EL (electroluminescence) characteristics of the polymer LEDs (PLEDs) having amorphous carrier injection layers had been investigated. The p-a-Si:H and n-a-SiCGe:H films were used as the hole and electron injection layers, respectively in these in these PLEDs to replace the conventional organic carrier injection layers. A peak brightness of 6450 cd/m2 at an injected cur | en_US |