A vertical AlGaN DUV light-emitting diode fabricated by wafer bonding and sapphire thinning technology

Abstract

We demonstrate a vertical AlGaN DUV LED with an emission wavelength of 272 nm and submicron thickness. The device epilayers thickness is reduced to ~670 nm by a combination of wafer bonding and thinning techniques, and this results in the thinnest vertical DUV LED reported to date. A light-emitting surface with root mean square value of 74.7 nm is also induced by thinning process without any other surface-roughing treatments. An n-contact electrode with a mesh geometry is adopted to expose the emission region, while the bottom metal electrode functions as a reflector to reflect downward-propagating light in an upward direction.

Exfoliation mechanism of AlGaN-based thin films using heated-pressurized water

“…Consequently, a method for removing the insulating substrate and AIN layer is essential. Among these methods, laser lift-off (LLO), [8][9][10][11][12][13][14][15] electrochemical etching, 16) and grinding and polishing 17) have been reported to exfoliate sapphire substrates. These methods have been employed in operating vertical devices.…”

“…These methods have been employed in operating vertical devices. 8,[13][14][15][16][17] Furthermore, an approach that combines mechanical polishing and inductively coupled plasma (ICP) etching with SF 6 gas has also been reported as a method to exfoliate UV-C LEDs on a SiC substrate. 18) Meanwhile, the method for exfoliating these substrates has many issues.…”

Fabrication of vertical AlGaN-based ultraviolet-B laser diodes using a laser lift-off method

“…Among these methods, laser lift-off (LLO), [25][26][27][28][29][30][31][32] electrochemical etching, 33) grinding and polishing, 34) and heatedpressurized water 35,36) have been reported to exfoliate sapphire substrates. We focus on achieving LLO-based exfoliation at the 1 cm 2 square wafer level using AlGaN templates grown on periodic AlN nanopillars formed through inductively coupled plasma (ICP) etching and nanoimprinting on sapphire substrates.…”

A method for exfoliating AlGaN films from sapphire substrates using heated and pressurized water

“…However, it is essential to exfoliate insulating sapphire or AlN substrates to realize vertical devices for UV light-emitting devices. Among these methods, LLO, [12][13][14][15][16][17][18][19][20] electrochemical etching, 21) and grinding and polishing 22) have been reported as methods for exfoliating sapphire substrates. Furthermore, the operation of vertical devices using these methods have been demonstrated.…”

“…Furthermore, the operation of vertical devices using these methods have been demonstrated. 13,[18][19][20][21][22] Another approach, combining mechanical polishing and inductively coupled plasma (ICP) etching with SF 6 gas, was reported for separating UV-C LEDs with AlN buffers fabricated on SiC substrates. 23) However, these methods have serious barriers to practical application, such as difficulty in increasing the wafer diameter and poor reproducibility.…”