STABLE AND EFFICIENT CATHODOLUMINESCENCE AND PHOTOLUMINESCENCE FROM ULTRATHIN POROUS SILICON LAYERS

Ultrathin porous Si layers (UPSLs) prepared on n-Si in aqueous NH4F so lution and oxidized in air were investigated with cathode- (CL), photo - (PL) and electroluminescence (EL) and have been compared with conven tionally prepared thick per-Si layers. The nanoporous structures were controlled with high-resolution scanning electron microscopy. Infrared spectroscopy was used for native oxide analysis. The luminescence pro perties of UPSLs were characterized by unusual high stability while co nventionally prepared per-Si showed strong luminescence degradation. T he CL spectra of UPSLs showed three peaks at 300, 400 and 560 nm and a shoulder about 620 nm. The PL and EL spectra of UPSLs were peaked at 620 and 800 nm, respectively. The role of native oxide formation for s table per-Si luminescence is discussed.