1
|
Ahmad Fajri FA, Mukherjee A, Naskar S, Ahmad Noorden AF, Abass A. A scattered volume emitter micropixel architecture for ultra efficient light extraction from DUV LEDs. Sci Rep 2024; 14:14108. [PMID: 38898079 PMCID: PMC11187205 DOI: 10.1038/s41598-024-64689-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 06/12/2024] [Indexed: 06/21/2024] Open
Abstract
Deep ultraviolet light-emitting diodes (DUV LEDs) typically suffer from strong parasitic absorption in the p-epitaxial layer and rear metal contact/mirror. This problem is exacerbated by a substantial portion of the multiple quantum well (MQW) emissions having a strong out-of-plane dipole component, contributing to emission in widely oblique directions outside the exit cone of the front semiconductor emitting surface. To address this, we propose an architecture that leverages such a heavily oblique angular emission profile by utilizing spaced-apart or scattered volume emitter micropixels that are embedded in a low-index dielectric buffer film with a patterned top surface. This approach achieves high light extraction efficiency at the expense of enlarging the effective emission area, however, it does not require a high-index (e.g., sapphire) substrate or a lens or a nanotextured epi for outcoupling purposes. Hybrid wave and ray optical simulations demonstrated a remarkable larger than three to sixfold increase in light extraction efficiency as compared to that of a conventional planar LED design with a sapphire substrate depending on the assumed epi layer absorption, pixel size, and ratio of light emission area to the MQW active area. An extraction efficiency three times greater than that of a recent nanotextured DUV LED design was also demonstrated. This architecture paves the way for DUV LEDs to have a plug efficiency comparable to that of mercury lamps while being significantly smaller.
Collapse
Affiliation(s)
- Faris Azim Ahmad Fajri
- ams OSRAM Group, Leibnizstraße 2, Regensburg, Germany.
- Centre for Advanced Optoelectronics Research, Kulliyyah of Science, International Islamic University Malaysia, Kuantan, Pahang, Malaysia.
| | | | - Suraj Naskar
- ams OSRAM Group, Leibnizstraße 2, Regensburg, Germany
| | - Ahmad Fakhrurrazi Ahmad Noorden
- Centre for Advanced Optoelectronics Research, Kulliyyah of Science, International Islamic University Malaysia, Kuantan, Pahang, Malaysia
| | - Aimi Abass
- ams OSRAM Group, Leibnizstraße 2, Regensburg, Germany
| |
Collapse
|
2
|
Jorudas J, Pashnev D, Kašalynas I, Ignatjev I, Niaura G, Selskis A, Astachov V, Alexeeva N. Green Removal of DUV-Polarity-Modified PMMA for Wet Transfer of CVD Graphene. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:4017. [PMID: 36432303 PMCID: PMC9697087 DOI: 10.3390/nano12224017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 11/02/2022] [Accepted: 11/13/2022] [Indexed: 06/16/2023]
Abstract
To fabricate graphene-based high-frequency electronic and optoelectronic devices, there is a high demand for scalable low-contaminated graphene with high mobility. Graphene synthesized via chemical vapor deposition (CVD) on copper foil appears promising for this purpose, but residues from the polymethyl methacrylate (PMMA) layer, used for the wet transfer of CVD graphene, drastically affect the electrical properties of graphene. Here, we demonstrate a scalable and green PMMA removal technique that yields high-mobility graphene on the most common technologically relevant silicon (Si) substrate. As the first step, the polarity of the PMMA was modified under deep-UV irradiation at λ = 254 nm, due to the formation of ketones and aldehydes of higher polarity, which simplifies hydrogen bonding in the step of its dissolution. Modification of PMMA polarity was confirmed by UV and FTIR spectrometry and contact angle measurements. Consecutive dissolution of DUV-exposed PMMA in an environmentally friendly, binary, high-polarity mixture of isopropyl alcohol/water (more commonly alcohol/water) resulted in the rapid and complete removal of DUV-exposed polymers without the degradation of graphene properties, as low-energy exposure does not form free radicals, and thus the released graphene remained intact. The high quality of graphene after PMMA removal was confirmed by SEM, AFM, Raman spectrometry, and by contact and non-contact electrical conductivity measurements. The removal of PMMA from graphene was also performed via other common methods for comparison. The charge carrier mobility in graphene films was found to be up to 6900 cm2/(V·s), demonstrating a high potential of the proposed PMMA removal method in the scalable fabrication of high-performance electronic devices based on CVD graphene.
Collapse
Affiliation(s)
- Justinas Jorudas
- THz Photonics Laboratory of Optoelectronics Department, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Daniil Pashnev
- THz Photonics Laboratory of Optoelectronics Department, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Irmantas Kašalynas
- THz Photonics Laboratory of Optoelectronics Department, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Ilja Ignatjev
- Department of Organic Chemistry, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Gediminas Niaura
- Department of Organic Chemistry, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Algirdas Selskis
- Department of Structural Analysis of Materials, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Vladimir Astachov
- Department of Physical Technologies, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| | - Natalia Alexeeva
- THz Photonics Laboratory of Optoelectronics Department, Center for Physical Sciences and Technology (FTMC), Saulėtekis Ave. 3, LT 10257 Vilnius, Lithuania
| |
Collapse
|