The effect of dry etching condition on the performance of blue micro light-emitting diodes with reduced quantum confined Stark effect epitaxial layer
Jeong‐Hwan ParkWentao CaiHeajeong CheongYasuhisa UshidaDa‐Hoon LeeYuto AndoYuta FurusawaYoshio HondaDong‐Seon LeeTae‐Yeon SeongHiroshi Amano
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Abstract:
As the size of micro light-emitting diodes (μLEDs) decreases, μLEDs encounter etching damage especially at the sidewalls that critically affects their properties. In this study, we investigated the influence of etching bias power (Pbias) on the performance of μLEDs and found that the current–voltage and light output–current characteristics of μLEDs were enhanced when Pbias was reduced. It was shown that at low Pbias, the chemical reaction between etching gas and gallium nitride, rather than ion sputtering, dominated the etching process, leading to low plasma damage and rough surface morphology. Additionally, to understand the etching-induced surface roughening behaviors, various substrates with different threading dislocation densities were treated at low Pbias. It was found that for the sample (with p-contact size of 10 × 10 μm2), the efficiency droop was approximately 20%, although the current reached 10 mA due most probably to the suppressed polarization effect in the quantum well. It was further observed that the external quantum efficiency (EQE) was dependent on Pbias, where the lowest Pbias yielded the highest maximum EQE, indicating that the plasma damage was mitigated by reducing Pbias. Optimization of dry etching and polarization-suppression conditions could pave the way for realizing high-performance and brightness μLEDs for next-generation displays.Keywords:
Quantum Efficiency
Dry etching
Dry etching characteristics of Cr films were investigated and some improvements have ben done with magnetically enhanced reactive ion etching (MERIE) system. Clear field patterns and ark field ones exposed on thin EB resists, whose thickness was less than 300 nm, were etched. Although there had been some difficulties in etching of clear-field pattens with SAL-601, these situations were much improved with an appropriate etching condition of magnetic field. It was found that magnetic field intensity affected Cr etching distributions very much. In marked contrast to the above results, MFI condition showed little contributions to the etching distribution of dark field patterns exposed on ZEP- 7000. It was shown that some waveforms of magnetic field could be effective to improve the etching characteristics for the plate whose etching area was extremely small. Etching characteristics for these extremely varied Cr-loaded are considered through the above etching results. Discussions about more useful dry etching process with MERIE system are also described.
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An advanced photomask dry etching system (NLDE-9035 Prototype) has been evaluated. This system adopts new plasma source NLDE, and has a 230 mm mask capability. In this experiment, etching uniformity, selectivity and etching pattern profile were mainly evaluated. Etching uniformity of 20 nm (range) was obtained and good pattern fidelity was confirmed.
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Selective etching is an important step in GaAs process. As the wet－ etching leads to undercut,poor selectivity and unrepeatable etching rate. It is necessary to research the dry etching. Although RIE and MERIE dry etching can be used for selective etching, they can cause serious damage, which affects the performance of devices and MMIC. ICP (inductive couple plasma) is a new method for low damage, high etching rate and high selective etching . In this paper, the selective etching of GaAs/AlGaAs is presented. The etching selectivity ratio of GaAs to AlGaAs is over 840:1 .
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There are two ways in fabricating grating1 one is wet-etching, the other is dry-etching. In this paper, the two methods will be compared in the last ,we have fabrticated 1st order grating usingdry etching.
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For etching of III-nitride materials, reactive ion etching (RIE) methods based on mixture gas such as Ch4/H2 and chloride gases are usually used. Although the etching speed of Cl2-based dry etching is usually higher than that of CH4-based dry etching, CH4-based dry etching is superior to Cl2-based dry etching from the viewpoint of being easier to handle and being less toxic and corrosive.
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When pattern size on the mask is getting smaller, wet etching can not control the CD well enough and it is also difficult to add CD bias by using wet etch, especially at the contact layer. Dry etching process is therefore used to meet these requirements. This paper is to report the problems we have encountered during the development of dry etching process and to introduce a two-step, wet then dry etching process, which we used to solve these problems.
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We demonstrate a significant quantum efficiency enhancement of InGaN red micro-light-emitting diodes (μLEDs). The peak external quantum efficiency (EQE) of the packaged 80 × 80 μm2 InGaN red μLEDs was largely increased to 6.0% at 12 A/cm2, representing the significant process in exploring the efficiency of InGaN red μLEDs. The improvement of the EQE is attributed to the significant enhancement of the quantum efficiency, which is confirmed by the electron–hole wavefunction overlap in the InGaN quantum well from the band gap simulation and the photoluminescence intensity ratio at room temperature/low temperature. Ultrasmall 5 × 5 μm2 InGaN red μLEDs were also obtained, which show a high peak EQE of 4.5%. This work demonstrates a simple approach to achieving highly efficient InGaN red μLEDs, which are very promising candidates for ultrasmall red μLEDs required by AR/VR displays.
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Single LiNbO3 (LNO) crystals are widely utilized in surface acoustic wave devices, optoelectronic devices, and novel ferroelectric memory devices due to their remarkable electro-optic and piezoelectric properties, and high saturation and remnant polarizations. However, challenges remain regarding their nanofabrication that hinder their applications. The prevailing etching techniques for LNO encompass dry etching, wet etching, and focused-ion-beam etching, each having distinct merits and demerits. Achieving higher etching rates and improved sidewall angles presents a challenge in LNO nanofabrication. Building upon the current etching researches, this study explores various etching methods using instruments capable of generating diverse plasma densities, such as dry etching in reactive ion etching (RIE) and inductively coupled plasma (ICP), proton exchange-enhanced etching, and wet chemical etching following high-temperature reduction treatment, as well as hybrid dry and wet etching. Ultimately, after employing RIE dry etching combined with wet etching, following a high-temperature reduction treatment, an etching rate of 10 nm/min and pretty 90° sidewall angles were achieved. Furthermore, high etching rates of 79 nm/min with steep sidewall angles of 83° were obtained using ICP dry etching. Additionally, using SiO2 masks, a high etching rate of 108 nm/min and an etching selectivity ratio of 0.86:1 were achieved. Distinct etching conditions yielded diverse yet exceptional results, providing multiple processing paths of etching for the versatile application of LNO.
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Plasma Etching
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