GaN-based LEDs grown on 6-inch diameter Si (111) substrates by MOVPE

The issues and challenges of growing GaN-based structures on large area Si substrates have been studied. These include Si slip resulting from large temperature non-uniformities and cracking due to differential thermal expansion. Using an A1N nucleation layer in conjunction with an AlGaN buffer layer for stress management, and together with the interactive use of real time in-situ optical monitoring it was possible to realise flat, crack-free and uniform GaN and LED structures on 6-inch Si (111) substrates. The EL performance of processed LED devices was also studied on-wafer, giving good EL characteristics including a forward bias voltage of ∼3.5 V at 20 mA from a 500 μm × 500 μm device. © 2009 SPIE.

InGaN/GaN LEDs grown on Si(111): Dependence of device performance on threading dislocation density and emission wavelength

We demonstrate the growth of crack-free blue and greenemitting LED structures grown on 2-inch and 6-inch Si(111) substrates by metalorganic vapour phase epitaxy (MOVPE), using AlN nucleation layers and AlGaN buffer layers for stress management. LED device performance and its dependence on threading dislocation (TD) density and emission wavelength were studied. Despite the inherently low light extraction efficiency, an output power of 1.2 mW at 50 mA was measured from a 500 μm square planar device, emitting at 455 nm. The light output decreases dramatically as the emission wavelength increases from 455 nm to 510 nm. For LED devices emitting at similar wavelength, the light output was more than doubled when the TD density was reduced from 5×1 09 cm-2 to 2×109 cm-2. Our results clearly show that high TD density is detrimental to the overall light output, highlighting the need for further TD reduction for structures grown on Si. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Scanning transmission electron microscopy investigation of the Si(111)/AlN interface grown by metalorganic vapor phase epitaxy

The structure and chemistry of the interface between a Si(111) substrate and an AlN(0001) thin film grown by metalorganic vapor phase epitaxy have been investigated at a subnanometer scale using high-angle annular dark field imaging and electron energy-loss spectroscopy. 〈1120̄〉AlN ∥ 〈110〉Si and 〈0001〉AlN ∥ 〈111〉 Si epitaxial relations were observed and an Al-face polarity of the AlN thin film was determined. Despite the use of Al deposition on the Si surface prior to the growth, an amorphous interlayer of composition SiNx was identified at the interface. Mechanisms leading to its formation are discussed. © 2010 American Institute of Physics.

Si（111）衬底上ZnO薄膜的磁控溅射法制备及表征

采用磁控溅射法在(111)单晶硅衬底上沉积了ZnO薄膜，并研究了退火温度对ZnO薄膜晶体质量、晶粒度大小、应力和光致发光谱的影响。X射线衍射(XRD)表明薄膜为高度c轴择优取向。不同退火温度下的ZnO薄膜应力有明显变化。应力分布最为均匀的退火温度为500℃。室温下对ZnO薄膜进行了光谱分析，可观测到明显的紫光发射(波长为380nm左右)。实验结果表明，用磁控溅射法在单晶硅衬底上能获得高质量的ZnO薄膜。

退火对Si（111）衬底上ZnO薄膜的结构和发光特性的影响

采用磁控溅射法在硅（111）衬底上制备了C轴高度取向的ZnO薄膜，并研究了退火温度和氧气气氛对ZnO薄膜晶体质量、晶粒度大小和光致发光谱的影响。X射线衍射表明，所有薄膜均为高度C轴择优取向，当退火温度低于900℃时，随着退火温度的升高，薄膜的取向性和结晶度都明显提高。室温下对ZnO薄膜进行了光谱分析，退火后的样品均可观测到明显的紫光发射。在一定的退火温度范围内，还可以观测到明显的紫外双峰。空气中退火的样品，当退火温度达到或高于600℃还可观测到绿光发射。实验结果表明，发光峰强度随退火温度和氧气气氛不同而不