【作者】 李金钗；

【导师】 康俊勇；

【作者基本信息】 厦门大学 ， 微电子学与固体电子学， 2008， 博士

【摘要】 Ⅲ族氮化物半导体在短波长高亮度发光二极管、高功率激光器、高灵敏度光探测器、以及高温大功率电子器件等方面有着广泛的应用前景。不同于传统的Ⅲ-Ⅴ族化合物半导体,纤锌矿结构的Ⅲ族氮化物半导体具有极强的自发极化和压电极化效应。极化效应在Ⅲ族氮化物的应用中起着双刃的作用,既有其危害处也有其得利处。对Ⅲ族氮化物半导体中的极化场加以调控,避其短扬其长,是人们渴望深入了解的课题。本论文围绕Ⅲ族氮化物半导体的极化效应和极化场调控,结合第一性原理计算方法、MOVPE生长技术、材料的结构和性能测试,着重从理论设计和MOVPE外延生长两方面开展了系统的研究,主要取得如下研究成果:首次提出并构建了Mg和Si定位共掺GaN结构,以期实现局域极化场的调制。通过第一性原理计算模拟Mg和Si定位共掺GaN的电子结构发现,定位共掺的Mg和Si杂质做为一个整体,对导电并无贡献,而是在GaN中形成了一个局域的极化场,在一定程度上提高了Mg的溶解度,减小了Mg受主激活能。首次提出并构建了Mg-和Si-8共掺AlGaN/GaN超晶格结构,实现了对超晶格的能带调制。第一性原理计算模拟的Mg-和Si-δ共掺AlGaN/GaN超晶格能带结构表明,在AlGaN/GaN超晶格的界面处分别插入Mg和Si的δ掺杂层,改变了超晶格中的内建电场,导致能带弯曲程度急剧增大。根据所设计的Mg-和Si-δ共掺超晶格结构,采用MOVPE技术外延生长了Mg-和Si-δ共掺p型AlGaN/GaN超晶格。Hall效应与光致发光谱测试结果表明,相比于Mg调制掺杂超晶格结构,Mg-和Si-δ共掺超晶格结构更有效地减小了Mg受主激活能,提高了Mg掺杂效率。进一步将该超晶格结构应用于深紫外LED的p型导电层,成功制备了Ⅰ-Ⅴ特性良好、电致发光主波长短至213 nm,且发光较强的深紫外发光二极管。提出并构建了Mg掺杂的InGaN/GaN量子阱结构,通过掺杂实现了对量子阱极化场乃至量子能级的调制。第一性原理计算模拟Mg掺杂的InGaN/GaN量子阱的能带结构表明,在InGaN阱区内掺入Mg杂质,削弱了量子阱中的极化场,导致导带与价带边的弯曲均有不同程度的减小,量子阱有效禁带宽度从0.98 eV“恢复”至1.09 eV。根据理论设计,采用MOVPE技术外延生长了未掺杂和Mg掺杂InGaN/GaN多量子阱。通过电致发光谱的研究厘清了InGaN/GaN多量子阱的量子能级间的电子跃迁发光机制。在高注入电流情况下,InGaN/GaN多量子阱中出现了电子势阱中第一电子能级到空穴势阱中第一重空穴能级(1e-1hh)和第二重空穴能级(1e-2hh)的两电子跃迁发光峰。进一步将Mg掺杂InGaN量子阱应用于蓝光LED中,有效地减小了极化场,调节了量子能级位置,进而改变了量子阱发光波长,提高了波长稳定性。更多还原

【Abstract】 Ⅲ-nitride semiconductors are very promising materials for their applications in optoelectronic devices(both emitters and detectors) and high power/temperature electronic devices.Being non-centro-symmetric and high degree ionicity,wurtziteⅢ-nitrides exhibit strong spontaneous and piezoelectric polarization effects,which influence carrier distributions,electric fields,and consequently a wide range of optical and electronic properties ofⅢ-nitrides and devices.In order to study the polarization effect onⅢ-nitrides,and to exploit the polarization field to advantage in nitride semiconductors and device engineering,comprehensive theoretical designs and heteroepitaxial growth of structuralⅢ-nitrides have been performed by the first-principles simulation and MOVPE technique.The site-selective codoped configurations have been designed and simulated for the first time by the first-principles calculation method to modify the polarization field in GaN.As indicated by the calculated electronic structures,the site-selective codoped Mg and Si dopants induce a localized polarization field in GaN,which will enhance the Mg concentration and reduce the activation energy of Mg acceptor.Mg- and Si-δ-codoped AlGaN/GaN superlattices(SLs) have been proposed and designed for the first time to modify the polarization field.The simulated results of the SLs structures show that conspicuous band bending occurs in the Mg- and Si-δ-codoped SLs,which indicates that the polarization field in SL has been intensified.Accordingly, the Mg- and Si-δ-codoped p-type AlGaN/GaN SLs have been grown by MOVPE.The hole concentrations and mobilities in the Mg- and Si-δ-codoped SLs have been measured to be larger than that of modulation-doped SL by Hall effect.Furthermore,by applying the Mg- and Si-δ-codoped SLs as the p-type layers,we have successfully fabricated deep UV-LED with superior current-voltage characteristics and high electroluminescence(EL) intensities of the wavelength down to 213 nm.Mg doped InGaN/GaN quantum well(QW) has been designed to modify the polarization field and the quantized levels in QW.The decrease band bending and the enlargement of the effective band gap in Mg-doped QW indicate that the polarization field has been reduced by Mg dopant.Accordingly,the undoped and Mg doped InGaN/GaN MQWs have been grown by MOVPE.At high injection-current level,two distinct EL emission peaks associated with the quantized level transitions are investigated in both undoped and Mg doped MQWs.Moreover,the energies of both two peaks in Mg-doped MQWs are higher,while the energy separation between them is smaller than that in undoped MQWs.These facts indicate that the quantized levels are modified by Mg dopant due to the reduction of polarization field.更多还原