An n-sheet, state-space ACTFEL device model.

摘要

The objective of the research presented in this thesis is to develop, implement, and demonstrate the utility of an n-sheet, state-space alternating-current thin-film electroluminescent (ACTFEL) device model. In this model, the phosphor layer is discretized into n + 1 layers, with band-to-band impact ionization, space charge creation/annihilation, and luminescent impurity excitation/de-excitation occurring only at n sheets between the n + 1 layers. The state-space technique is a structured approach in which the ACTFEL device physics implementation is separated from the ACTFEL measurement circuit electrical response, resulting in a set of coupled, first-order differential equations which are numerically evaluated. The device physics implementation begins with electron injection from phosphor/insulator interfaces and band-to-band impact ionization. Phosphor layer space charge generation via band-to-band impact ionization and subsequent hole trapping, trap-to-band impact ionization, and shallow donor trap emission are then added to the model. Finally, impact excitation and radiative relaxation are added to the model to account for ACTFEL device optical properties.; The utility of the n-sheet, state-space ACTFEL device model is demonstrated in simulations which verify hypotheses regarding ACTFEL device measured characteristics. The role of phosphor layer hole trapping and subsequent thermionic emission in SrS:Cu ACTFEL device EL thermal quenching is verified via simulation. Leaky ACTFEL device insulators are shown to produce high luminance but low efficiency. A novel space charge estimation technique using a single transferred charge curve is presented and verified via simulation. Hole trapping and trap-to-band impact ionization are shown to produce realistic overshoot in C − V curves, and each results in a different phosphor layer space charge distribution. DC coupling of the sense capacitor used in the measurement circuit to the applied voltage source is required for the generation of ACTFEL device electrical offset, as verified by simulation. Shallow donors are identified as a probable SrS:Ce ACTFEL device leakage charge mechanism. A field-independent emission rate time constant model is shown to yield realistic ZnS:Mn ACTFEL device leakage charge trends.