Analysis of electroluminescence spectra from high optical-power density forward-biased silicon-led in standard CMOS technology

Abstract

A Si-LED with high-power density p+-n junction and wedge-shaped electrodes was fabricated by standard complementary metal oxide-semiconductor (CMOS) process, and its electroluminescence (EL) spectra were measured at different forward currents. By studying the EL spectra, two interesting phenomena were found. One was that the main peak of EL spectra transited from long wavelength (1135 nm) to short wavelength (1078 nm) along with the forward current increased. The other was that two light emission peaks with energy larger than band gap (Eg) were observed. For the first time, reasonable explanations to the two phenomena were given. Here, the peak shift is attributed to that, with forward current increased, the electron-hole pair recombination of the bound excitons without assist of phonons, increases faster than that of those bound or free excitons with assist of phonons. And the existence of two energy-high light emission peaks is resulted from that, under strong electric field, hot holes absorb one or two phonons from the crystal lattice and then recombine with electrons in conduction band.