【作者】 梁晓祯；

【导师】 杨林安；

【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2011， 硕士

【摘要】 第三代半导体材料GaN具有击穿电压高、迁移率高、电子饱和速度大等优良特点。近年来AlGaN/GaN HEMT的研究已经取得很大的进展,但应力诱导的压电问题一直是AlGaN/GaN HEMT的主要问题之一。In组分为17%的InAlN能够与GaN完全匹配,消除压电极化,提高器件的可靠性。而InAlN/GaN HEMT的研究相对较少,尤其是在国内InAlN/GaN HEMT的研究才刚起步。在此背景下,本文主要针对InAlN/GaN HEMT进行了研究。首先,本文完成了InAlN/GaN HEMT器件的研制,并测得有较好的直流和小信号特性。还对漏端的工艺进行了改进,研制出肖特基作漏端的AlGaN/GaN HEMT器件。肖特基作漏的器件在具有与常规器件相同功能的基础上,还使得击穿电压明显增大。而且,首次发现漏端肖特基的势垒高度越大,器件的击穿电压越大。其次,对自主研制的InAlN/GaN异质结的陷阱进行了研究,通过电流崩塌和钝化前后材料方块电阻的变化,发现InAlN材料表面可能存在陷阱,并且利用肖特基的电容-电压的测试方法,对InAlN/GaN的陷阱密度进行了估算,然后采用低温退火的方法使得陷阱有一定的减少。此外,还研究了不同温度下退火对器件其它特性的影响。最后,对InAlN/GaN HEMT器件的陷阱与温度的关系进行了研究,通过对肖特基的变温测试发现,肖特特表面陷阱或者势垒层陷阱随温度的升高而增多,并且这些陷阱的增多会使得器件的电流崩塌也变得严重。另外,分析了温度对器件直流特性的影响,随温度升高,二维电子气浓度变化不大,迁移率减小,材料的方阻、欧姆接触、器件的输出和转移都有不同程度的退化。更多还原

【Abstract】 As the third-generation semiconductor, GaN has lots of advantages as high breakdown voltage, mobility and saturation velocity and so on. Although the research of AlGaN/GaN HEMT has great development in the past years, the piezopolarization induced by the strain of the lattice mismatched heterostructure is still one of the key problems. At 17% In-content InAlN can be grown lattice matched to GaN, with no piezopolarization, and improve the reliability. But less study have been taken on InAlN/GaN heterostructure in past years, especially this is just the beginning in our state, so this paper will focus on this point.Firstly, this paper presents the InAlN/GaN HEMT with well DC and small-signal characteristics made by ourselves. Then, improve the drain structure and investigate AlGaN/GaN HEMT with schottky drain. This device has significantly high breakdown voltage, and the other characters are as well as common device. Also, the breakdown voltage of this device increases with the schottky barrier height of the drain was studied firstly.Secondly, the trap of the InAlN/GaN HEMT was investigated. Traps on the surface of InAlN were found by the current collapse effect and difference of material sheet resistance after passivation, also the approximate density was calculated by the schottky capacity changed with voltage. These traps were reduced with the method of low temperature anneal. Moerover, the infection of anneal to other characters of device has been analysed.Finally, the heat-temperature characteristics of InAlN/GaN HEMT including surface trap and DC are measured. New traps of surface or barrier were induced by higher temperature, which lead current collapse more serious. Also, the DC peformance and mobility have degenerated for increased temperature, as sheet resistance, contect resiatance, output current and trans-conductance, while the 2DEG has little change.更多还原