Study On Ohmic Contact Mechanism And Electrode Design Of N-plane GaN-based LED

The development of high-quality n-type Ga N-based LED Ohmic electrodes requires metal electrodes to be in contact with N?nitrogen?polar plane n-type Ga N?N-Ga N?,and preparing N-Ga N-based LED Ohmic electrodes with low resistance and high stability has been a major problem in this field.Prof.Fengyi Jiang of Nanchang University found that adding nitrogen vacancy?V_N?on the surface of Ga N can improve the Ohmic characteristics of metal and N-Ga N contact.Insight into the modulation mechanism of defects on N-Ga N-based Ohmic electrodes is of great scientific value and practical significance for improving the performance of N-Ga N-based LED devices.The purpose of this paper is to theoretically reveal the physical nature behind this experimental phenomenon.This paper uses first-principles methods to find that defects can modulate the Schottky barrier height of Al?111?/N-Ga N interface.The physical mechanism of the Ohmic contact of the defect modulation interface was revealed from the two aspects of the interface electronic structure characteristics and the carrier transport characteristics.On this basis,a guiding scheme is provided for the experimental preparation of low resistance and high stability N-Ga N-based n-type Ohmic electrodes.The main contents of the study are as follows:According to the atomic arrangement characteristics of N-Ga N,two types of Al?111?/N-Ga N interface models are established in this paper,which are named A-type and B-type respectively.The macroscopic average electrostatic potential method is used to calculate the barrier height.The n-type Schottky barrier heights of A-and B-type interfaces are 1.722e V and 1.615e V,respectively.The results show that the n-type Schottky barrier of the two types of interfaces are reduced by the donor defects like the V_N and oxygen dopant at the nitrogen site?O_N?,and enhanced by the accept defects like the gallium vacancy(V_Ga)and the O_N-V_Ga complex.Moreover,the Schottky barrier height of the B-type interface is always lower than that of the A-type interface.The conclusion is consistent with the experimental phenomenon that increasing V_Nconcentration can improve the performance of N-Ga N-based LED electrode.The analysis of electron structure and carrier transport characteristics shows that the defect and interface geometry can not only turn the height of the Schottky barrier but also affect the tunneling of the interface electron.Based on the mechanism of interface composition and carrier transport affecting the height of the Schottky barrier,an experimental scheme of introducing donor defect on the basis of the B-type model is proposed,which provides a design idea and theoretical basis for realizing high-quality N-Ga N-base LED Ohmic contact in experiments.