Electrical Performance Simulation And Physical Property Research On InAlN/AlN/GaN Heterostructure

Due to the strong spontaneous polarization and piezoelectric polarization of group III nitride materials and heterostructure, it can produce very strong built-in electric field, even in the case of not doping, it can form more than 1013 cm-2 sheet density of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructure interface. In addition, the Ⅲ-nitride semiconductors have excellent electrical properties such as high saturation velocity, high breakdown voltage, and the big band offset energy in heterostructure interface, therefore, they are considered as a system of ideal material in high temperature, high power and high frequency electronics. In recent years, the lattice matched In0.17 Al0.83 N/AlN/GaN high electron mobility transistor (HEMT) attracts a lot of attention, and it is expected to replace the AlGaN/GaN HEMT structure in some applications. Since InAlN/GaN heterostructure has the characteristics of the lattice match, there exsits only spontaneous polarization in heterostructre in theory, it would overcome the crystalline quality degradation accompany strain relaxation, guarantees the high two-dimensional electron gas concentration; The device is very prominent characteristics of DC and RF characteristics, but also can overcome the difficulty that can’t fabricate high performance HEMT devices based AlxGa1-xN/GaN heterostructure (x>=0.4) in high aluminum components.In this paper, we focus on the InAlN/GaN heterosturcture, using one-dimensinal schrodinger and poisson equations, study the band structure and the 2DEG distribution of the two kinds of heterostructure nominal InAlN/AIN/GaN/AlGaN/GaN and InAN/AlN/GaN/InGaN/GaN theoretically, and characterize and analyze several nearly lattice matched InAlN/AlN heterojunction materials which growthed by MBE or MOCVD respectively. The main contents and conclusions are as follows:1、 The 2DEG properties with the thickness of the inserted layer AlN of nearly lattice matched InAIN/AIN/GaN heterostructure have been investigated. When the barrier layer thickness fixed, with the thickness of the inserted AlN increase, the concentration of 2DEG will increase at first, and then reduce, the critical thickness of AlN about 2.43nm is obtained. Simulations are mainly focused on the InAlN/AlN/GaN heterostructures with AlGaN and InGaN back barrier respectively. For the AlGaN back barrier structure, the concentration of 2DEG in AIN/GaN will decrease with Al content increase in AlGaN, and GaN channel layer conduction band will be raised with increase of Al content in AlGaN, to a certain extent, increase the restriction of 2DEG. For the InGaN back barrier structure, the concentration of 2DEG in AIN/GaN increase with the increase of the InGaN components In in InGaN at first, and then decrease, GaN channel layer of conduction band will be raised with the increase of components In in InGaN, can increase the restriction of 2DEG2、The MOCVD-grown InAlGaN/AIN/GaN heterostructure has been studied with XPS technique. The metal elements (Al, In, Ga) composition and the binding energy in InAlGaN film layer along with the change of thickness of thin film are focused. It is found that with increasing InAlGaN film thickness, Al element content increased gradually, and the Ga gradually reduces, but the content of elements In content basically remain unchanged, the change is caused by the " compositional pulling effect"; with the sputtering time increase, the bind energy of metal elements are moving in the direction of low energy first,and the move in the dirction of high enrgy, think that the former is mainly influenced by external oxygen environment, while the latter is mainly because of nitrogen vacancy in material.3、Two MBE-grown heterostructures that InAlN/AIN/GaN and InAlN/AIN/GaN/InGaN/GaN have been characterized by AFM and TEM. The calculated dislocation density of the two samples by AFM and TEM, the V-pits density of InAIN/AIN/GaN is 8*106cm-2, the InAlN/AIN/GaN/InGaN/GaN dislocation density and V-pits density are about 1.1* 109 cm-2 respectively. It is found that the insertion of InGaN back barrier leads the crystalline degration.