The Japanese research team has manufactured a vertical deep ultraviolet emitting semiconductor laser device based on AlGaN, which is expected to be applied in fields such as laser processing

Recently, a Japanese research team has developed a vertical deep ultraviolet emitting semiconductor laser device based on AlGaN, which is expected to be applied in laser processing, biotechnology, and medical fields.

As is well known, ultraviolet (UV) is an electromagnetic wave with a wavelength range of 100 to 380nm. These wavelengths can be divided into three regions: UV-A (315-380 nm), UV-B (280-315 nm), and UV-C (100-280 nm), with the latter two regions containing deep ultraviolet light.

Laser sources emitted in the ultraviolet region, such as gas lasers and solid-state lasers based on yttrium aluminum garnet laser harmonics, can be widely used in biotechnology, skin disease treatment, UV curing processes, and laser processing. However, such lasers have drawbacks such as large volume, high power consumption, limited wavelength range, and low efficiency.

In recent years, with the continuous development of manufacturing technology, the development of high-performance semiconductor lasers that generate light through injection current has been promoted. This includes ultraviolet light emitting devices based on the semiconductor material aluminum gallium nitride AlGaN. However, their maximum optical output power in the deep ultraviolet region is only about 150mW, far lower than the power required for medical and industrial applications. Increasing the injection current of the device is crucial for improving output power. This requires increasing the device size while ensuring uniform current flow in the device.

In this research context, a Japanese research team led by Professor Yuanming Iwao from the Department of Materials Science and Engineering at Nagasaki University has successfully developed a high-performance vertical AlGaN type UV-B semiconductor laser diode. The study was published in the journal Applied Physics Letters.

Professor Yanwu Yuanming once stated that existing deep ultraviolet lasers based on AlGaN utilize insulating materials such as sapphire and AlN to obtain high-quality crystals. But because current flows laterally in these devices, scientists have explored vertical devices to improve their optical output. In a p-n junction, the p-electrode and n-electrode face each other. However, in the past few years, vertical configuration has been used to achieve high-power semiconductor devices. However, in terms of semiconductor lasers, the development of this configuration has been stagnant and has not yet been achieved in deep ultraviolet light emitting devices based on aluminum nitride. To this end, researchers first manufactured high-quality aluminum nitride on a sapphire substrate. Subsequently, periodic aluminum nitride nanopillars were formed and laser structures based on aluminum nitride were deposited.

The research team utilized innovative laser peeling technology based on pulsed solid-state lasers to peel the device structure off the substrate. They also developed a semiconductor process to manufacture the electrodes, current limiting structures, and insulation layers required for laser oscillation, and developed a splitting method using blades to form excellent optical resonators. The AlGaN based deep ultraviolet B semiconductor laser diode thus manufactured has novel and unique characteristics. It can operate at room temperature, emitting extremely sharp light at a wavelength of 298.1nm, with a clear threshold current and strong transverse polarization characteristics. The researchers also observed the unique spot like far-field mode of the laser, confirming the oscillation of the device.

This study indicates that vertical devices can provide high current for the operation of high-power devices. In the future, it will play a greater role in new cost-effective manufacturing processes for electric vehicles and artificial intelligence. And researchers also hope that vertical ultraviolet lasers based on aluminum nitride can have practical applications in medical and manufacturing fields.

Source: Sohu