LED epitaxial wafer grown on Si substrate through L-MBE and MOCVD technologies, and preparation method for LED epitaxial wafer

Abstract

The invention discloses an LED epitaxial wafer grown on a Si substrate through L-MBE and MOCVD technologies. The LED epitaxial wafer comprises the Si substrate, and a monocrystal Al thin film, an AlGaN buffer layer, an n-GaN layer, an InGaN / GaN MQWs quantum well layer and a p-GaN layer which are grown on the Si substrate in sequence, wherein the content of the Al content in the AlGaN buffer layer is gradually decreased in a direction from the monocrystal Al thin film to the n-GaN layer; the monocrystal Al thin film is grown by adopting an L-MBE method; and the AlGaN buffer layer, the n-GaN layer, the InGaN / GaN MQWs quantum well layer and the p-GaN layer are grown by an MOCVD method. The invention also discloses a preparation method for the LED epitaxial wafer. The LED epitaxial wafer prepared by the invention is high in crystal quality, low in defect density, and excellent in electric and optical properties.

Description

technical field [0001] The invention relates to the field of LED epitaxial wafers, in particular to an LED epitaxial wafer grown on a Si substrate by using L-MBE and MOCVD techniques and a preparation method thereof. Background technique [0002] Light-emitting diodes (LEDs) made of GaN and its related Group III semiconductor materials are widely used in indoor lighting, commercial lighting, engineering lighting and other fields. However, the cost problem has always been an important factor that has plagued the expansion of LED technology. [0003] Due to the lack of mature GaN substrate preparation technology, commercial GaN-based LEDs are generally fabricated by heteroepitaxial methods. As substrates commonly used to grow GaN, sapphire, SiC, and Si have all realized the preparation of device-level LEDs, but the epitaxial layer growth problems brought about by their respective substrate materials still need to be continuously overcome. Sapphire has stable physical and che...

AI Technical Summary

Problems solved by technology

However, the cost problem has always been an important factor that has plagued the expansion of LED technology.

However, although Si has many advantages, the quality of GaN single crystal thin films prepared on Si substrates is not as good as that of sapphire substrates, and there are still many difficulties in the preparation of device-level Si-based LEDs.

First, the lattice mismatch between Si and GaN is still large (about 16%), comparable to that of sapphire, and the defects in GaN epitaxial layers grown on Si are not reduced by orders of magnitude

Secondly, the thermal expansion coefficient of Si is 2.61×10-6 / K, and the thermal mismatch with GaN is as high as 114%, much higher than that of sapphire (about -25.5%), which will lead to huge tensile stress in the epitaxial layer, thus It is more likely to cause cracks in the epitaxial layer

In addition, the following problems exist in the growth of AlN, AlGaN and GaN using traditional MOCVD (metal organic chemical vapor deposition) technology: 1) Ammonia gas (NH 3 ), due to the large bond energy of Si-N, the Si substrate easily forms an amorphous SixNy layer at the interface when it encounters active N, which seriously affects the quality of the obtained GaN-based LED device

2) During the epitaxial growth of AlN and AlGaN layers, there are serious parasitic pre-reactions, that is, TMAl and NH 3 It is easy to nucleate in the gas phase in the reaction chamber to form AlN solid particles. On the one hand, it reduces the growth rate of AlN. On the other hand, the formed solid particles fall to the surface of the film and easily form defects.

3) The mobility of Al atoms on the surface of the film is low, so it is difficult to grow AlN and AlGaN films with high quality and high Al composition using traditional growth techniques

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