Study Of Three-Dimensional P-n Junction In GaN/Si-Based Light-Emitting Diodes With V-Shaped Pits

Ga N/Si-based semiconductors have been successfully used to fabricate high-efficiency blue,green,and yellow light-emitting diodes(LEDs)with the feature of single light emission face.The large V-shaped pits,grown around the dislocations in this new basic optoelectronic material,are believed to have greate impact on the device performance.In this work,a series of experiments and simulation studies on the growth mechanism of the V-shaped pit and its three-dimensional p-n junction behavior are investigated.The following innovative research results are obtained:1.The formation and evolution mechanism of V-shaped pits in Ga N/Si films have been revealed.By creatively comparing the bulk and the boundary of grown Ga N films,the mechanism of formation and filling-up of V-shaped pit is attributed to decreased and increased growth rate around dislocation sites,respectively,which successfully explain the influences of temperature,growth rate,indium content on the growth behavior of V-shaped pits in Ga N films.2.The ABC-model for analyzing the efficiency of Ga N LEDs has been optimized.The dependence of the radiative recombination rate on lattice temperature and carrier concentration is obtained at high injections.The new model gives that,even at the same temperature,the radiative recombination rate has an upper limit when the carrier concentration is high enough.It provides a new reference to understand the carrier recombination and generation mechanism in Ga N LEDs.3.A method for quickly fitting of the quantum efficiency is developed by using semiconductor simulation tool ATLAS to analyze the Ga N/Si-based LED with V-shaped pits.With precise geometry modeling of V-shaped pit,by adjusting material parameters and physical models,simulation with good approach to the experiment results,at high current densities,on I-V characteristic,internal quantum efficiency and spectra shape have been achieved.4.Simulation results show that the depletion region of the lateral p-n junction is thinner than than that of the vertical p-n junction in the Ga N/Si-based LED with V-shaped pits,which could be the cause of operating voltage reduction by V-shaped pit.Furthermore,it is observed that the large V-shaped pits can reduce the photoluminescence intensity of the last quantum well.The reason can be attributed to the large lateral built-in electric field of the three-dimensional p-n junction,which separates the photogenerated carriers and reduces the recombination probability.5.The dependence of optoelectric performances on the barrier growth temperature of Ga/Si-based LED with V-shaped pit is studied.It is observed that the barrier temperature will seriously affect the sharpness of the well/barrier interface,which subsequently affects the efficiency of LEDs.Results show that the optimized barrier growth temperature is about 150~oC more than the well growth temperature.The optimized ABC-model above is used to simulate these behaviors and make a reasonable explanation.This work's major research results have been adopted by the National Institute of LED on Silicon Substrate in Nanchang University,which makes substantive effects and improves the overall performance of Ga N/Si-based LEDs.Some of the results are inconvenient to elaborate here due to the relevant invention patents have not been disclosed.This work has reference value and great significance for the material growth,optoelectric performance and physics study of Ga N/Si-based LED with V-shaped pits.