News Article
Verticle reveals copper-based hexagonal UV-LED chip
The firm has extended its product line in gallium nitride (GaN) based UV-LEDs
Verticle's new hexagonal shaped UV chip incorporates a copper substrate to enable a higher current.
Despite many advantages, the main drawback of UV-LEDs is lower optical power due to lower internal quantum efficiency (IQE).
Since improving the IQE of UV epitaxial wafers is a long-term prospect, an alternative way to boost UV-LED power is to drive more current in.
However, heat generation is a big issue with high current drive. What's more, aluminium containing UV epitaxial wafers are more resistive than blue, meaning thermal management of UV-LEDs is more critical. This makes one of the main challenges lowering the junction temperature in UV-LEDs.
An SEM image of the hexagonal UV-LED chip
UV light emitting from the chip
In order to operate at higher current injection conditions and dissipating heat more efficiently, Verticle’s UV-LED chip uses a copper substrate. According to the firm, as shown in the figure below, its copper based vertical chip’s thermal resistance (Rth) is 2K/W lower than for a GaN-on-silicon vertical chip.
Thermal resistance and junction temperature of GaN-on-silicon and GaN-on-copper vertical LEDs as a function of injection current (at 250C).
As a result, Verticle maintains that the junction temperature (Tj) of GaN-on-copper is lower than for GaN-on-silicon. Also, the junction temperature difference is 20C at 350 mA current injection between two chips. And the difference becomes larger (60C) at a 1A current injection.
What's more, Verticle claims its UV-LED chip can be driven at a higher current than other vertical chips constructed with different substrate materials.
Verticle also says its GaN-on-copper UV-LED chips do not saturate over 1A, while GaN-on-tungsten and GaN-on-sapphire UV-LED chips start to saturate after 500mA. This means that the GaN-on-copper chips have a higher heat dissipation capability compared to GaN on other substrates.
This could mean that copper based UV-LED chips have distinct advantages for applications where high current injection and good thermal properties are required.
A graph illustrating the firm's hexagonal UV-LED chip performsnce is shown below. Data was taken for a 45 mm size chip with radiant fluxes measured at 416mW at 350mA current injection, 787mW at 700mA, and 1.025mW at 1A for the 392 nm wavelength, respectively.
Radiant flux vs. current: 1) GaN-on-copper vertical UV-LED, 2) GaN-on-tungsten vertical UV-LED, and 3) GaN-on-sapphire lateral UV-LED. Bare UV-LED chips were attached on 5050 metal lead frame without molding. To eliminate wavelength dependency on radiant flux, 390 ~ 395nm UV-LED chips were used.
Verticle believes an additional benefit of its hexagonal chip is a higher extraction efficiency once it is packaged with a circular lens. The reason for this is that the hexagonal chip has a near circular beam profile when it is packaged with a circular lens. So there is less of a dark spot than there is in rectangular chips.
This makes Honeycomb LEDs useful for optic design with a circular lens system where a near circular beam profile is required for various package and module applications.
Verticle’s hexagonal UV-LED chip samples are available upon request from the company's website.
Verticle Inc.is located in the Silicon Valley, California with production facilities in Korea. The firm specialises in manufacturing vertical type LED chips using a patented copper substrate and Chemical Chip Separation Technology.
Despite many advantages, the main drawback of UV-LEDs is lower optical power due to lower internal quantum efficiency (IQE).
Since improving the IQE of UV epitaxial wafers is a long-term prospect, an alternative way to boost UV-LED power is to drive more current in.
However, heat generation is a big issue with high current drive. What's more, aluminium containing UV epitaxial wafers are more resistive than blue, meaning thermal management of UV-LEDs is more critical. This makes one of the main challenges lowering the junction temperature in UV-LEDs.
An SEM image of the hexagonal UV-LED chip
UV light emitting from the chip
In order to operate at higher current injection conditions and dissipating heat more efficiently, Verticle’s UV-LED chip uses a copper substrate. According to the firm, as shown in the figure below, its copper based vertical chip’s thermal resistance (Rth) is 2K/W lower than for a GaN-on-silicon vertical chip.
Thermal resistance and junction temperature of GaN-on-silicon and GaN-on-copper vertical LEDs as a function of injection current (at 250C).
As a result, Verticle maintains that the junction temperature (Tj) of GaN-on-copper is lower than for GaN-on-silicon. Also, the junction temperature difference is 20C at 350 mA current injection between two chips. And the difference becomes larger (60C) at a 1A current injection.
What's more, Verticle claims its UV-LED chip can be driven at a higher current than other vertical chips constructed with different substrate materials.
Verticle also says its GaN-on-copper UV-LED chips do not saturate over 1A, while GaN-on-tungsten and GaN-on-sapphire UV-LED chips start to saturate after 500mA. This means that the GaN-on-copper chips have a higher heat dissipation capability compared to GaN on other substrates.
This could mean that copper based UV-LED chips have distinct advantages for applications where high current injection and good thermal properties are required.
A graph illustrating the firm's hexagonal UV-LED chip performsnce is shown below. Data was taken for a 45 mm size chip with radiant fluxes measured at 416mW at 350mA current injection, 787mW at 700mA, and 1.025mW at 1A for the 392 nm wavelength, respectively.
Radiant flux vs. current: 1) GaN-on-copper vertical UV-LED, 2) GaN-on-tungsten vertical UV-LED, and 3) GaN-on-sapphire lateral UV-LED. Bare UV-LED chips were attached on 5050 metal lead frame without molding. To eliminate wavelength dependency on radiant flux, 390 ~ 395nm UV-LED chips were used.
Verticle believes an additional benefit of its hexagonal chip is a higher extraction efficiency once it is packaged with a circular lens. The reason for this is that the hexagonal chip has a near circular beam profile when it is packaged with a circular lens. So there is less of a dark spot than there is in rectangular chips.
This makes Honeycomb LEDs useful for optic design with a circular lens system where a near circular beam profile is required for various package and module applications.
Verticle’s hexagonal UV-LED chip samples are available upon request from the company's website.
Verticle Inc.is located in the Silicon Valley, California with production facilities in Korea. The firm specialises in manufacturing vertical type LED chips using a patented copper substrate and Chemical Chip Separation Technology.
