Calculation Of Band Structures For Ⅲ-Nitride Semiconductors And Investigation Of The Polarization Properties Of Ⅲ-Nitride-Based Leds

Ⅲ-nitride semiconductors,represented by GaN,have attracted much attention in the field of optoelectronic devices due to their various properties such as adjustable bandgap.This thesis focuses on the basic properties（band structure characteristics）of low-dimensional III-nitride materials based on first-principles calculations.Using TCAD software,the device characteristics（polarized emission characteristics）of III-nitride-based LEDs are further studied.The main conclusions are as follows:Based on the study of the band structure characteristics of bulk III-nitride materials(InN,GaN,AlN,In_xGa_1-xN and Al_xGa_1-xN),further research has been conducted on the band structure characteristics of low-dimensional single-layer planar structures and folded structures passivated by H atoms.The results show that InN in a single-layer planar structure has a direct bandgap,while GaN and AlN have an indirect bandgap.GaN and InN in a single-layer folded structure have a direct bandgap,while AlN has an indirect bandgap.In_xGa_1-xN in both single-layer planar and folded structures have a direct bandgap,while Al_xGa_1-xN in a single-layer planar structure has an indirect bandgap,and the bandgap of folded Al_xGa_1-xN changes from direct to indirect when the Al fraction reaches 0.75.For low-dimensional bilayer In_xGa_1-xN and Al_xGa_1-xN,different atomic substitutions can also significantly affect the band structure characteristics when the metal ion composition is constant,providing a new avenue for further manipulation of the band characteristics of low-dimensional III-nitride semiconductor materials.After studying the basic optoelectronic properties of AlGaN-based LEDs,we further investigated their polarized light emitting properties,as well as the influence of the length of the p-GaN layer.The research results show that the far-field light intensity distribution characteristics vary significantly with changes in the Al composition,but the spatial distribution charactreristics of light intensity is obvious,which is mainly related to the different photon polarization degrees in the active region and the wavelength of the traced light rays.The preliminary research results also indicate that the polarization properties of the light emission are significantly affected by the length of the p-GaN layer,and the directional distribution of light intensity in space is obviously different.This has certain guiding significance for further optimizing the LED device structure and improving the light extraction efficiency.