Semipolar (112) InGaN light‐emitting diodes grown on chemically–mechanically polished GaN templates

Abstract

Abstractauthoren InGaN multiple quantum well light‐emitting diodes (LEDs) were grown on chemically–mechanically polished (112―2) GaN templates (up to 100 mm diameter wafers) by metalorganic vapour phase epitaxy. Initial GaN overgrowth on the polished templates in nitrogen ambient maintained the polished surface. The peak emission wavelength of the LEDs varied from 445 to 550 nm. In contrast to the simultaneously grown LEDs on as‐grown templates, the LEDs on polished templates have very smooth surface morphology, uniform luminescence, and higher output power. Fluorescence images of 445 nm LEDs grown on (a) as‐grown and (b) polished (112―2) GaN templates.

Role of substrate quality on the performance of semipolar (112¯2) InGaN light-emitting diodes

“…56 Additionally, the rough surface morphology of the PSS-LED (Fig. 1) is another issue as it can cause nonuniform carrier distribution 21,44 and compositional fluctuations. 21 It has been previously found that polished PSS-GaN substrates can strongly enhance the luminescence uniformity of QWs and the performance of PSS-LEDs.…”

“…1) is another issue as it can cause nonuniform carrier distribution 21,44 and compositional fluctuations. 21 It has been previously found that polished PSS-GaN substrates can strongly enhance the luminescence uniformity of QWs and the performance of PSS-LEDs. 21 The internal absorption has been found to be significant in nitrides for emission energy below the GaN band-edge due to background doping, leading to an increase in electronic transitions between donor-acceptor levels and structural defects.…”

“…These stripes are believed to develop during coalescence from irregularities at the meeting facets of adjacent GaN template structures, 13,14 which normally result in a rough surface morphology resulting in a non-uniform luminescence of overgrown InGaN QWs. 21 In contrast, the FWHM PL map of the Bulk-LED is uniform. The average FWHM PL of the Bulk-LED was estimated to be 78.8 6 1.7 meV slightly smaller than the PSS-LED of 80.6 6 4.6 meV.…”

“…19 However, this prediction needs to be further confirmed experimentally. [19][20][21] In this paper, we report semipolar (11 22) InGaN LEDs emitting at $430 nm grown simultaneously on PSS-and Bulk-GaN substrates. The optical properties and performance of the LEDs were assessed.…”

“…Details of the LED growth conditions are reported elsewhere. 21 The composition of the InGaN QW active region was examined using a PANalytical X'pert triple-axis highresolution X-ray diffraction system with a CuKa 1 source. The In-content of the QWs was estimated to be about 14%.…”