Band gap shift in the GaN∕AlN multilayers on the mesh-patterned Si(111)

Abstract

The band gap shift in the 80×80μm2 crack-free GaN∕AlN multilayers on the mesh-patterned Si(111) has been characterized by cathodoluminescence (CL) and Raman techniques. The GaN band gap derived from CL spectra depends on the spatial point inside a mesh, which changes from 3.413eV (at center) to 3.418eV (at edge) and to 3.426eV (at corner). The band gap shift is attributed to the variation of tensile stress inside the mesh, confirmed by Raman mapping. The shift of GaN band gap per unit stress is determined to be 0.03eV∕GPa.

A low damage GaN-based light-emitting diode with textured/inclined sidewalls and an air–buffer layer

“…Moreover, ununiform stress variation induced by lattice mismatch as well as different positions on a mesa region, always happen on the semiconductor-based heterojuntion which is grown on a mesh-patterned substrate [9]. It is believed that this effect become more obvious on the sapphire/GaN interface, and when the periodicity of patterns is only 2 lm (pattern spacing) in this work.…”

“…Lateral etching usually occur at chemical-weak defect sites, such as the juncture of protrudent sapphire and GaN epilayer. Where chemical bonds may be relatively weaker due to the stress variation [9] and etches along the GaN crystal surface. The actual ratio between lateral and vertical etching rate possibly depends on the material parameters (doping density, type of doping, and crystal quality of the local regions) Hence, the ununiformly triangular-shaped cones are presented on the PSS, as shown in Fig.…”

“…The scale of cones dominantly depends on the local strengths of chemical bonds formed on GaN/sapphire junctures, which decreases with increasing the strength of a local chemical bond [9]. Clearly, the KOH etchant etches through GaN layer until the chemical-inert crystal surface is exposed which yields an air-buffer layer between GaN epilayer and sapphire substrate.…”

Characteristics of a Low-Damage GaN-Based Light-Emitting Diode Using a KOH-Treated Wet-Etching Approach

“…13) Many edges with about 120 angle are produced along the specific direction h1 1 100i, where photons introduced within MQW have more opportunities to scatter into the air, as mentioned above. Moreover, lateral etching usually occur at chemical-weak defect sites, such as the juncture of protrudent sapphire and GaN epilayer where chemical bonds may be relatively weaker due to the stress variation 14) and etches along the GaN crystal surface. Hence, the ununiformly triangular-shaped cones are presented on the PSS, as shown in the inset of Fig.…”

“…The scale of cones dominantly depends on the local strengths of chemical bonds formed on GaN/sapphire junctures, which decreases with increasing the strength of a local chemical bond. 14) Figure 3 illustrates scanning electron microscopy (SEM) cross-section views of triangular-shaped cones. The insets of Fig.…”