Full text loading...
(a) PL spectra measured with the Si CCD. (PL-Si-nc/Si) PL emitted from the LED surface (inset on the left). Because both the Si-nc thin film and the Si substrate are excited by the laser, they both contribute to the PL. (PL-Si) PL from the bare Si substrate (inset at the center) used for the LED; here the PL spectrum is scaled so that it has the same peak intensity at 1100 nm as the Si-nc/Si PL. (PL-Si-nc) Si-nc PL is obtained after subtracting the Si PL in red from Si-nc/Si PL in black. The Si-nc/Si PL spectrum is shifted vertically for clarity. The drop in intensity at wavelengths longer than 1000 nm is due to the cutoff response of the Si CCD. (b) Current-voltage characteristics of the Si-nc/Si LED. Forward bias corresponds to a positive voltage on the p-type substrate as shown in the inset.
(a) Forward-bias EL spectra at currents of 5, 10, and 20 mA. The solid black curve is PL of the Si substrate. The EL and PL spectra are measured using the InGaAs detector. (b) Integrated EL intensity as a function of current.
(a) EL of the LED under reverse bias at currents of 5, 10, and 20 mA. The spectra are obtained using the Si CCD. (b) Integrated EL intensity as a function of current.
Schematic band diagrams of the device under forward bias (a) and reverse bias (b) at a small current of . The 6 V reverse bias and the 2.5 V forward bias voltages are deduced from the I-V curve in Fig. 1(b). The work function of ITO (4.7 eV) and band offsets between and Si are taken from Refs. 5, 7, and 13–15. Note that at the reverse bias of 6 V the interface between the Si-nc thin film and the Si substrate is depleted of electrons. As shown in Fig. 1(b) a larger reverse bias voltage is needed to induce EL, because as explained in the text the latter originates from electrons tunneling from the inversion layer at the thin film-substrate interface.
Article metrics loading...