Optical emission characteristics of semipolar (1\,1\,\bar{2}\,2) GaN light-emitting diodes grown on m-sapphire and stripe-etchedr-sapphire

Abstract

We demonstrate the growth and optical characterization of semipolar (1 1 2 2) GaN light-emitting diodes (LEDs) on sapphire utilizing two distinct heteroepitaxial growth methodologies. The properties of semipolar (1 1 2 2) LEDs are analyzed by the simultaneous growth of LED structures on templates prepared by both two-step growth on m-sapphire and selective growth on etched r-plane sapphire. Typically, growth on m-sapphire yields a high density of microstructural defects and surface morphological features which complicate the understanding of emission properties in devices. In this study, we find improved spectral properties of devices grown on etched r-sapphire due to improved surface roughness and microstructural quality (x-ray diffraction rocking curves of 280-550 arcsec for on-axis (1 1 2 2) and off-axis (1 0 1 n), n = 0-5 diffractions), and reveal that the commonly observed broad emission and sub-bandgap peak in semipolar LEDs on sapphire are caused by a tunneling-assisted radiative recombination mechanism.

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

“…Recently, patterned r ‐plane (102) sapphire substrates have been employed to grow high quality semipolar (112) GaN templates (pss‐GaN templates) . Despite their good crystallinity, the rough surface morphology with a high density of micro‐sized arrow‐head features resulted in a non‐uniform photoluminescence (PL) of QWs and electroluminescence (EL) of LEDs (). To overcome that problem, chemical–mechanical polishing (CMP) can be used to planarize directly the template surface ().…”

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

“…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.…”

Complete orientational access for semipolar GaN devices on sapphire

“…The restriction of producing orientations by finding new epitaxial relations is thus lifted, and instead is designed by the choice of sapphire substrates, which are grown in bulk boules and can be sliced in any direction in wafers of diameters up to 8″ diameter or even larger. With this technique, it can be expected that semipolar GaN orientation with any index ( hkil ), l > 0 can be achieved, as demonstrated in the specific cases of () , () , () , () , and () .…”

“…Of the three types of orientations classified in Fig. , devices have been demonstrated directly on only the first type, naturally occurring semipolar facets, such as () , and () . Of the second type, artificial semipolar planes, devices have only been shown by further thick HVPE growth and polish process to similarly produce quasi‐bulk semipolar GaN substrates .…”