Carrier transport in porous silicon light-emitting devices

This work presents a comprehensive investigation of carrier transport properties in light-emitting porous silicon (LEPSi) devices. Models that explain the electrical characteristics and the electroluminescence properties of the LEPSi devices are developed. In metal/LEPSi devices, the forward current density–voltage (J–V) behavior follows a power law relationship (J∼Vm), which indicates a space charge current attributed to the carriers drifting through the high resistivity LEPSi layer. In LEPSi pn junction devices, the forward J–V behavior follows an exponential relationship (J∼eeV/nkT), which indicates that the diffusion of carriers makes a major contribution to the total current. The temperature dependence of the J–V characteristics, the frequency dependence of the capacitance–voltage characteristics, and the frequency dependence of the electroluminescence intensity support the models. Analysis of devices fabricated with a LEPSi layer of 80% porosity results in a relative permittivity of ∼3.3, a carrier mobility of ∼10−4 cm2/V s, and a free carrier concentration of ∼1013 cm−3.