Field emission from surface textured extraction facets of GaN light emitting diodes

We report on the field emission properties of GaN LED surfaces. The textured extraction facet acts both as light scattering layer in order to increase the light extraction efficiency of the LED as well as nanostructured cathode surface for the field emission (FE) of electrons. The LED emits blue light with a peak wavelength of around 450 nm. The FE properties were investigated by a scanning microscope. Integral measurements as well as regulated voltage scans for 1 nA FE current over an area of 400 × 400 μm² were used to investigate both overall and local FE properties. A high number of well-distributed emitters with an average field enhancement factor β of 85 and stable integral emission currents up to 100 μA at an electric field of ~ 80 V/μm (Ø_anode = 880 μm) were found. Photo-field-emission spectroscopy (PFES) using a tunable pulsed laser revealed an enhanced photo absorption of the InGaN/GaN quantum well structures near the emission wavelength of the LED (<;3.5 eV), whereas at high photon energies (>4.1 eV) photoemission from the GaN surface was observed.