高纯半绝缘GaN单晶材料的制备及其电学输运性质研究

High purity semi insulating（HPSI） GaN is an ideal substrate for the preparation of high integration and high power RF microwave devices, which has wide applications in phased array radar, 5G mobile communication, and so on. But the study on HPSI-GaN has not yet started, because the background impurity concentration is too high, and also we have little knowledge on the deep level defects in GaN. Recently, the GaAs and SiC material both realized the HPSI electrical property, which points out the way for HPSI-GaN. In this project,we aim at the preparation of HPSI-GaN by hydride vapor phase epitaxy. We will study on the formation mechanism and control mechanism of point defects in the nonequilibrium growth mode, and also the main factors concern about the impurity incorporation efficiency. Based on the two studies above, the HPSI-GaN will be prepared through the compensation of residual shallow level impurities by deep level point defects. After that, the electrical transport mechanism of HPSI-GaN will be carefully studied, and also the influence of high temperature, high electrical field and light on transport property will be considered to find the failure mechanism in severe cases, which are benificial for the development of high performance devices based on the HPSI-GaN.

高纯半绝缘（HPSI）GaN是制备高集成度大功率射频微波器件的理想衬底材料，在相控阵雷达、5G移动通信等领域有重要应用。但由于GaN背底杂质浓度太高，并且缺乏对GaN材料内部深能级点缺陷的理解，高纯半绝缘GaN的研究尚未起步。目前，与GaN性质相近的GaAs和SiC等材料都实现了高纯半绝缘，这为HPSI-GaN的开发指明了方向。本项目基于氢化物气相外延生长技术（HVPE）来制备高纯半绝缘GaN单晶衬底，研究非平衡气相生长模式下GaN内部点缺陷的形成机理与调控机制，探索GaN材料内部杂质掺入效率的影响因素，通过调控深能级点缺陷浓度以补偿背底剩余浅能级杂质来实现高纯半绝缘；研究HPSI-GaN的电学输运特性，探索高温、高场、光照等条件对其输运性质的影响，阐明恶劣使役条件下HPSI-GaN的失效机制，为下游基于HPSI-GaN衬底的高性能器件的开发奠定基础。

高纯半绝缘GaN材料能够抑制Fe掺杂GaN材料在器件中引入的电流崩塌、恢复时间长、迁移率低等问题，是制备高电子迁移率晶体管、光导开关器件、声表面波器件的理想衬底材料。本项目通过采用惰性耐高温的陶瓷材料制作反应器，并降低背底Si、O等浅能级施主在GaN材料中的掺入效率，成功实现了电阻率高于 1e6 ohm-cm 的高纯半绝缘 GaN 单晶衬底的制备，并将背底的Si、O等主要的浅能级施主杂质降低到了GDMS（辉光放电质谱仪）的探测限（<0.05 ppm）之下。所有元素中只有B、Mg、Al、Mn、Fe高于探测限，其重量百分比分别只有0.03、0.06、0.37、0.02、0.05 ppm，绝大多数杂质浓度<1e15 cm-3。通过本项目实施，开发出了具有自主知识产权的高纯半绝缘GaN 单晶衬底材料制备技术路线，为我国宽禁带半导体光电子和微电子器件的发展提供新的材料支撑。