Impact of the gate fabrication process of light emitting capacitors based on silicon-rich oxide: Low voltage electroluminescence

We study the effect of the gate fabrication process on the electro-optical properties of metal-oxide-semiconductor (MOS) capacitors with a silicon-rich oxide (SRO) film and n+ polysilicon (Poly-Si) layer as the active layer and gate electrode, respectively. Two sets of capacitors were fabricated changing the Poly-Si doping process. The first set was doped using a mixture of N2, O2 and PH4 at 1000 °C for 15 min. The second set was similarly doped but an additional re-diffusion process using only N2 and O2 at 1000 ᵒC for 20 min was carried out. The doping step causes diffusion of silicon (Si) atoms from a Poly-Si gate towards the SRO which binds to its microstructure forming Si0, Si2+, Si3+ states while the re-diffusion also causes a diffusion of phosphorus (P) atoms, forming P–Si bonds and generating a restructuring of the SRO. These changes determine the electro-optical properties of devices based on SRO. Capacitors with doped emit full area white electroluminescence (EL) observed a naked eye at ∼27 V (∼7 MV/cm) while capacitors with doped + re-diffusion emit orange-red EL spots at ∼ 6 V (∼1.5 MV/cm).