SiC MOSFET高温栅氧可靠性研究

碳化硅SiC(silicon carbide)具有优良的电学和热学特性,是一种前景广阔的宽禁带半导体材料。SiC材料制成的功率MOSFET(metal-oxide-semiconductor field-effect transistor)非常适合应用于大功率领域,而高温栅氧可靠性是大功率MOSFET最需要关注的特性之一。通过正压高温栅偏试验和负压高温栅偏试验对比了自研SiC MOSFET和国外同规格SiC MOSFET的高温栅氧可靠性。负压高温栅偏试验结果显示自研SiC MOSFET与国外SiC MOSFET的阈值电压偏移量基本相等,阈值电压偏移量百分比最大相差在4.52%左右。正压高温栅偏试验的结果显示自研SiC MOSFET的阈值电压偏移量较小,与国外SiC MOSFET相比,自研SiC MOSFET的阈值电压偏移量百分比最大相差11%。自研器件占优势的原因是在SiC/SiO2界面处引入了适量的氮元素,钝化界面缺陷的同时,减少了快界面态的产生,使总的界面态密度被降到最低。

SiC外延炉加热系统的设计

碳化硅材料是一种宽禁带半导体材料,其耐高温、耐高压的特性特别适合制作大功率半导体器件。近几年来,随着SiC器件生产工艺技术的突破,碳化硅器件得到了快速的发展,其相关设备也在不断开发并走向成熟。简要介绍了SiC外延生长设备中加热器的设计方法、温度控制以及温度均匀性调节方法,通过实验验证了温度均匀性及控制精度。

影响SiC外延生长速率的相关因素探讨

研制了水平热壁式外延沉积系统,设计了双加热器温控系统和水平三层流喷淋系统,介绍了温场和流场获得方法。在偏4°的Si面4H-SiC单晶衬底上进行了工艺验证。研究了生长温度、C/Si以及SiH_4流量对SiC外延生长速率的影响,通过主要参数的综合调整,生长出了表面光滑的SiC外延膜。

The Growth and Fabrication of InGaN/GaN Multi-Quantum Well Solar Cells on Si(111) Substrates

Metalorganic chemical vapor deposition of a crack-free mirror-like surface of InGaN/GaN MQWs on Si(111)substrate is demonstrated,and an InGaN/GaN MQWs solar cell device is fabricated.Photo response measurement of the solar cell devices shows that the fill factor FF=49.4%,open circuit voltage V_(oc)=0.32 V,and short circuit current J_(sc)=0.07 mA/cm^(2),under AM 1.5 G illumination.In order to analyze the influence of material quality on the performance of solar cells,XRD,SEM and Raman scattering experiments are carried out.It is found that insertion of a proper top AlN layer can effectively improve the material quality,and therefore enhance the photovoltaic performance of the fabricated device.

Enhanced performance of InGaN/GaN multiple quantum well solar cells with patterned sapphire substrate

In this paper, the enhanced performance of InGaN/GaN multiple quantum well solar cells grown on patterned sapphire substrates （PSS） was demonstrated. The short-circuit current （Jsc） density of the solar cell grown on PSS showed an improvement of 60%, compared to that of solar cells grown on conventional sapphire substrate. The improved performance is primarily due to the reduction of edge dislocations and the increased light absorption path by the scattering from the textured surface of the PSS. It shows that the patterned sapphire technology can effectively alleviate the problem of high-density dislocations and low Jsc caused by thinner absorption layers of the InGaN based solar cell, and it is promising to improve the efficiency of the solar cell.

The growth and characterization of GaN films on cone-shaped patterned sapphire by MOCVD

GaN films are grown on cone-shaped patterned sapphire substrates （CPSSs） by metal-organic chemical vapor deposition, and the influence of the temperature during the middle stage of GaN growth on the threading dislocation （TD） density of GaN is investigated. High-resolution X-ray diffraction （XRD） and cathodeluminescence （CL） were used to characterize the GaN films. The XRD results showed that the edge-type dislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates （CSSs）. Furthermore, when the growth temperature in the middle stage of GaN grown on CPSS decreases, the full width at half maximum of the asymmetry （102） plane of GaN is reduced. This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs. The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS, and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases.