Nitride deep-ultraviolet light-emitting diodes with microlens array

We report on the fabrication of 280-nm AlGaN-based deep-ultraviolet light-emitting diodes (UV LEDs) on sapphire substrates with an integrated microlens array. Microlenses with a diameter of 12μm were fabricated on the sapphire substrate by resist thermal reflow and plasma dry etching. LED devices were flip-chip bonded on high thermal conductive AlN ceramic submounts to improve the thermal dissipation, and the emitted UV light was extracted through the sapphire substrates. With the integrated microlens array, a 55% enhancement in the output power at 20-mA dc driving was achieved compared with the same LED without microlens. The light extraction enhancement is the result of the reduced internal reflections of the light caused by the microlens surface profile.

[1]  Erdan Gu,et al.  GaN micro-light-emitting diode arrays with monolithically integrated sapphire microlenses , 2004 .

[2]  S. Denbaars,et al.  Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening , 2004 .

[3]  Robert Kaplar,et al.  Room-temperature direct current operation of 290 nm light-emitting diodes with milliwatt power levels , 2004 .

[4]  Mim Lal Nakarmi,et al.  AlGaN-based ultraviolet light-emitting diodes grown on AlN epilayers , 2004 .

[5]  J. Lin,et al.  Nitride microlens arrays for blue and ultraviolet wavelength applications , 2003 .

[6]  K. H. Kim,et al.  III-nitride blue and ultraviolet photonic crystal light emitting diodes , 2004 .

[7]  Max Shatalov,et al.  AlGaN-based 280nm light-emitting diodes with continuous wave powers in excess of 1.5mW , 2004 .

[8]  Gustaaf Borghs,et al.  Impact of texture-enhanced transmission on high-efficiency surface-textured light-emitting diodes , 2001 .

[9]  Arpad Bergh,et al.  The Promise and Challenge of Solid-State Lighting , 2001 .

[10]  Hongxing Jiang,et al.  Enhanced light extraction in III-nitride ultraviolet photonic crystal light-emitting diodes , 2004 .

[11]  A W Lohmann,et al.  Scaling laws for lens systems. , 1989, Applied optics.

[12]  A. Scherer,et al.  30% external quantum efficiency from surface textured, thin‐film light‐emitting diodes , 1993 .

[13]  M. Asif Khan,et al.  High-efficiency 269 nm emission deep ultraviolet light-emitting diodes , 2004 .

[14]  E. Fred Schubert,et al.  Light-Emitting Diodes , 2003 .

[15]  Y. J. Sung,et al.  Refractive sapphire microlenses fabricated by chlorine-based inductively coupled plasma etching. , 2001, Applied optics.

[16]  Shuji Nakamura,et al.  The Blue Laser Diode: GaN based Light Emitters and Lasers , 1997 .