Method for preparing GaN-based photonic crystal LED based on nanoimprint lithography

Abstract

The invention discloses a method for preparing a gallium nitride (GaN)-based photonic crystal light-emitting diode (LED) based on nanoimprint lithography. The method comprises the following steps of: epitaxially growing an N-GaN layer, a multi-quantum well active region and a P-GaN layer on a sapphire substrate in turn, and forming a GaN-based LED epitaxial structure piece; (2) performing anti-sticking treatment on a hard template for nanoimprint; (3) preparing a software template with a complementary pattern of the hard template; (4) respectively evaporating a mask layer and a nanoimprint ultraviolet adhesive layer on the epitaxial structure piece; (5) performing ultraviolet imprint on an evaporated device, and demolding to form a pattern piece with photonic crystals; and (6) etching thepattern and performing subsequent treatment to obtain the photonic crystal LED. In the method, the nanoimprint ultraviolet adhesive layer and the evaporated mask layer are combined to serve as a mask, so that the problem of imprinting difficulties caused by the unevenness of the surface of the GaN epitaxial piece is solved; therefore, the effective hole depths of the photonic crystal are greater.

Description

technical field [0001] The invention belongs to the field of photoelectric device preparation, and in particular relates to a method for a GaN-based photonic crystal LED. Background technique [0002] There is a significant gap between the internal quantum efficiency and external quantum efficiency of traditional light-emitting diodes. The internal quantum efficiency of standard visible light-emitting diodes is close to 100%, while the external quantum efficiency is less than 5%. This is because the photons emitted by the active layer of the LED produce total reflection at the interface between the P-type layer and the air, and the critical angle is relatively small (θ≈23°), so that most photons cannot be emitted. In order to allow more light to escape and obtain high-efficiency light output, people have developed photonic crystal technology. [0003] The introduction of the photonic crystal structure can not only introduce the photonic band gap, suppress the spontaneous em...

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Problems solved by technology

[0002] There is a significant gap between the internal quantum efficiency and external quantum efficiency of traditional light-emitting diodes. The internal quantum efficiency of standard visible light-emitting diodes is close to 100%, while the external quantum efficiency is less than 5%.

[0006] The surface of traditional GaN epitaxial wafers is uneven. Through the scanning electron microscope (SEM) test, it is detected that the roughness of traditional GaN epitaxial wafers exceeds 50nm at around 100um, such as figure 1 As shown, photonic crystals were prepared on the surface by traditional nanoimprinting process such as figure 2 As shown, the effect is not good, the pattern of the prepared photonic crystal is poor, and its shape is similar to the surface roughening. Although it has the effect of improving the light output efficiency of LED, the effect is not obvious

The reason is that during the pattern transfer process of ultraviolet glue, due to the uneven surface, the etching rate of different heights of ultraviolet glue is different, which may easily cause incomplete removal of residual glue, and the etching selectivity ratio of ultraviolet glue and GaN material is small, which eventually leads to transfer The target pattern is deformed

Therefore, the greater the surface roughness of the embossing, the worse the quality of the photonic crystal pattern obtained after copying and transferring, which is not conducive to the significant improvement of the LED light extraction efficiency.

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