温度梯度对GaN热压电pn结电学性能的影响

热感应产生的极化电势可以改变压电半导体结构内的力电物理量,这在人工智能、微机电系统(MEMS)中极具应用价值.文章针对温度梯度作用下的氮化镓(GaN)压电pn结,采用二维压电半导体多场耦合方程和精确的热电物理边界条件,数值分析了温度梯度改变对GaN热压电pn结内极化强度、电势、电场、载流子分布及电流等物理场的影响.结果表明:由于温度梯度场和极化电荷之间存在耦合,热压电pn结电学性能对温度梯度高度敏感,由温度改变产生的热感应极化电荷可以有效调节该结构的开启电压和载流子传输特性,这为操控与温度相关的智能异质结器件电流传输提供了新的方法和理论指导.     

GaN/AlN量子点结构中的应变分布和压电效应

从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发,采用有限元方法计算了GaN/AlN量子点结构中的应变分布,研究了其自发极化、压电极化以及极化电荷密度.结果表明,应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化,使电子聚集在量子点顶部,空穴聚集在量子点下面的湿润层中,在量子点结构中产生显著的极化电场,并讨论了电场的存在对能带带边的形状以及能级分布的影响.     

GaN／AIN量子点结构中的应变分布和压电效应

从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发，采用有限元方法计算了GaN／AIN量子点结构中的应变分布，研究了其自发极化、压电极化以及极化电荷密度．结果表明，应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化，使电子聚集在量子点顶部，空穴聚集在量子点下面的湿润层中，在量子点结构中产生显著的极化电场，并讨论了电场的存在对能带带边的形状以及能级分布的影响．     

BNKABTx无铅压电陶瓷制备工艺研究

利用XRD、SEM等现代分析技术,研究了[Bi0.5(Na0.985-xKxAg0.015)0.5]0.94Ba0.06TiO3系无铅压电陶瓷的合成温度、烧成工艺条件对陶瓷微结构和压电性能的影响,同时研究了极化条件对材料压电性能的影响。结果表明,适当地提高合成温度有利于主晶相的形成,适当升高烧结温度有利于提高材料的压电性能。提高极化电压和极化温度,适当延长极化时间,有利于提高材料的压电性能,但过高的温度因受材料高温下退极化的影响而导致材料压电性能变差。     

GaN/AlN量子点结构中的应变分布和压电效应

从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发,采用有限元方法计算了GaN/AlN量子点结构中的应变分布,研究了其自发极化、压电极化以及极化电荷密度.结果表明,应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化,使电子聚集在量子点顶部,空穴聚集在量子点下面的湿润层中,在量子点结构中产生显著的极化电场,并讨论了电场的存在对能带带边的形状以及能级分布的影响.     

无铅Bi0．5（Na1-x—yKxLiy）0．5TiO3陶瓷的制备工艺研究

利用XRD等现代分析技术,研究了Bi0.5(Na1-x-yKxLiy)0.5TiO3系无铅压电陶瓷的合成温度,烧成工艺条件对陶瓷晶体结构和压电性能的影响.同时研究了极化工艺条件对材料压电性能的影响.结果表明,合成温度的提高有利于主晶相的形成,适当延长烧结保温时间有利于提高材料的压电性能.该体系随着K含量的增加,烧结温度提高及范围变窄.当提高极化电场和极化温度时,有利于压电性能的提高,但过高的温度因受材料高温下退极化的影响而导致材料压电性能变差.     

半导体技术

O4712007060630GaN/AlN量子点结构中的应变分布和压电效应/梁双,吕燕伍(北京交通大学物理系)//半导体学报.―2007,28(1).―42～46.从Ⅲ-Ⅴ族氮化物半导体压电极化对应变的依赖关系出发,采用有限元方法计算了GaN/AlN量子点结构中的应变分布,研究了其自发极化、压电极化以及极化电荷密度。结果表明,应变导致的压电极化和Ⅲ-Ⅴ族氮化物半导体所特有的自发极化将导致电荷分布的变化,使电子聚集在量子点顶部,空穴聚集在量子点下面的湿润层中,在量子点结构中产生显著的极化电场,并讨论了电场的存在对能带带边的形状以及能级分布的影响。图4表1…     

BNKABTx无铅压电陶瓷制备工艺研究

利用 XRD、SEM 等现代分析技术,研究了[Bi0.5(Na0.985-xKxAg0.015)0.5]0.94-Ba0.06TiO3系无铅压电陶瓷的合成温度、烧成工艺条件对陶瓷微结构和压电性能的影响,同时研究了极化条件对材料压电性能的影响。结果表明,适当地提高合成温度有利于主晶相的形成,适当升高烧结温度有利于提高材料的压电性能。提高极化电压和极化温度,适当延长极化时间,有利于提高材料的压电性能,但过高的温度因受材料高温下退极化的影响而导致材料压电性能变差。     

逆压电极化效应对AlGaN/GaN异质结2DEG特性的影响

从正-逆压电极化效应对GaN材料的影响出发,通过自洽求解一维Poisson-Schr(o)dinger方程,研究了逆压电极化效应对AlGaN/GaN异质结中2DEG浓度的影响.计算结果显示,逆压电极化明显影响2DEG性质,当Al组分x=0.3,AlGaN层厚度为20 nm时,不考虑逆压电极化,2DEG浓度为1.53×1013 cm-2;当等效外加电压分别为10和15 V时,2DEG浓度降低至1.04×1013cm-2和0.789×1013cm-2,可见当等效外电压由0～15 V变化时,2DEG浓度下降了48.4%.     

KNN基无铅压电陶瓷材料制备的研究进展

碱金属铌酸盐系的(K,Na)NbO_3(KNN)因其具有高压电常数(d_(33)),高机电耦合系数,高品质因数及高居里温度(T_C)而成为无铅压电材料研究的热点。为了探索高性能KNN无铅压电陶瓷材料制备及应用,该文综述了其相关制备工艺、性能特点,重点阐述了KNN系无铅压电材料的掺杂、烧结、极化及其对性能的影响,指出了KNN无铅压电陶瓷的掺杂改性及工艺优化研究是其有效的研究方向。     

Study of the polarizations of (Al,Ga,AlGa)N nitride compounds and the charge density of various interfaces based on them

The results of a theoretical study based on ab initio calculations of the polarization properties of AlN, GaN, and AlGaN semiconductors with the wurtzite structure are presented. The values of the spontaneous and piezoelectric polarizations, as well as the piezoelectric constants, are calculated for these nitride compounds. With the aim of further considering prospective heterostructures based on (Al,Ga,AlGa)N compounds, the charge densities at the AlN/GaN, AlGaN/AlN, and AlGaN/GaN interfaces and carrier concentration at the AlGaN/GaN heterointerface is estimated and compared with the experimental data.     

Design and realization of phase retardation-control polarization controllers based on artificial birefringence

Polarization controllers(PCs) are indispensable passive components for state of polarization(SOP) control in optical fiber communication systems.In order to overcome the disadvantages of existing polarization controller(PC),a novel PC based on the artificial birefringence is designed in this paper.The PC results from the concatenation of 3 phase retardation control units each of which consists of two polarization beam splitters,two prisms and one piezoz-lectric transducer(PZT) piezoelectric ceramic.The experimental results show that the proposed PC can convert an arbitrary input SOP to any expected output one with high accuracy under low control voltage.     

GaN材料系列的研究进展

ＧａＮ及其合金作为第三代半导体材料具有一系列优异的物理和化学性质，在光电子器件，高温大功率电子器件及高频微波器件应用方面具有广阔的前景，已成为当前高科技领域的研究重点，论述了这种材料的研究历史与发展现状，物理与化学性质，薄膜的生长方法及在光学电子和微电子器件应用于方面的研究进展。     

A Bamboo‐Like GaN Microwire‐Based Piezotronic Memristor

Bamboo‐like gallium nitride (GaN) microwires are synthesized via chemical vapor deposition (CVD) to fabricate piezotronic memristors. Defect boundary areas (DBAs) near the bamboo knots produce apparent switching between high and low resistance states upon sweeping of the magnitudes of the biased voltages across the GaN microwire‐based devices at room temperature. Furthermore, by coupling the piezoelectric and semiconducting properties in the GaN microwire, the piezotronic effect is introduced to effectively modulate the SET voltages via strain‐induced piezoelectric polarizations created at the DBA interface upon mechanical deformation. The experimental results indicate that the device remembered the most recent resistance states when the power is turned off, and the waveform is tunable because of the delayed switching effect. This work provides an alternative approach to the design and modification of memristors based on nanostructured piezoelectric semiconductors using the piezotronic effect.     

预应变InGaN/GaN多量子阱发光特性调控研究

为了减弱InGaN/GaN量子阱内的压电极化场,在蓝紫光InGaN/GaN多量子阱激光器结构中采用了预应变InGaN插入层,通过变温电致发光和高分辨X射线衍射测量研究了预应变插入层对量子阱晶体质量和发光特性的影响。实验结果显示,常温下有预应变层的量子阱电致发光谱积分强度显著提高。模拟计算进一步表明,预应变层对量子阱内压电极化场有调制效果,有利于量子阱中的应力弛豫,可以有效减弱量子限制斯塔克效应,有助于提高量子阱的发光效率。     

Scavenging Energy Sources Using Ferroelectric Materials

Ferroelectric materials have attracted interest for over a hundred years as a result of their spontaneous polarization and a polarization orientation that can be reversed by the application of an external electric field. In addition, the degree of polarization can be affected by external stimuli such as vibrations, stress, heat, and light. These properties enable ferroelectric materials to be used to fabricate nanogenerators, which are devices used in energy scavenging applications and provide an opportunity to obtain electrical energy from a variety of external stimuli. This review discusses the development of ferroelectric-based nanogenerators for scavenging mechanical, thermal, and solar energies through the piezoelectric effect, pyroelectric effect, and photovoltaic effect, respectively. The mechanisms of the effects and the pathways to optimize the output performance of the nanogenerators are analyzed in detail. Recent developments in energy harvesting using ferroelectric materials are discussed with the objective to motivate attention and efforts in this growing field.