Shukla, Abhinav (2020-08). Modelling and Simulation Study of Electro-thermal Characteristics and Emitted Light Characteristics in Solid State Incandescent Light Emitting Devices. Master's Thesis.
Thesis
Recently, researchers have reported a unique solid state incandescent light emitting device (SSI-LED) made from a simple MOS capacitor with an amorphous high-k gate dielectric thin film deposited on the p-type Si substrate. Other than lighting applications, SSI-LED is promising candidate for on-chip optical interconnects and nonvolatile memories. The study of such devices can play a crucial role in their incorporation in future electronic and optoelectronic applications. In this thesis, the electrothermal characteristics of the SSI-LED is studied using finite element modeling in COMSOL Multiphysics program. Temperature distributions within and around individual nano-resistors of different sizes distributed randomly in the gate dielectric of SSI-LED were obtained with optimized boundary conditions. The current density variation near the edge of the large nano-resistors affected the local temperature distribution across the cross-section of nano-resistors. The light filtration effect of ITO and a-Si:H thin films on the broad-band light emitted from the ZrHfO high-k dielectric based SSI-LED has been theoretically investigated and compared with the experimental observations. The deviation in peak wavelengths of computed spectra from experimental emission spectra suggested that the thin film filters above nano-resistors formed in the dielectric film might have a change in phase owing to the intense Joule heating during the passage of a large current. The broadband light spectrum emitted from the SSI-LED could be narrowed down with the addition of thin film filters, and the peak of the new spectrum was dependent upon the optical properties of the material of the filter. Light intensity distributions from nano-resistor based SSI-LED are also studied using physics-based analytical calculations. The inter-nanoresistor distance affected the resolvability of individual nano-resistor light sources. Formation of nano-resistor clusters and the presence of few large nano-resistors resulted in bright radiation spots observed at higher magnifications. Light from individual nano-resistors could not be resolved at lower magnifications. The device's center region was brightest, with light intensity diminishing uniformly in the radially outwards direction. The geometrical layout of the nano-resistors formed in the SSI-LED also affected the local light intensity distribution at higher magnifications.
