Reduced-stress GaN epitaxial layers grown on Si(111) by using a porous GaN interlayer converted from GaAs

Abstract

This paper reports the reduced-stress GaN epitaxial growth on Si (1 1 1) using a porous GaN interlayer which is formed from GaAs layer by a novel nitridation process. Initially a 2 μm thick GaAs layer is grown on a Si(1 1 1) substrate by MBE. Then, a GaN buffer layer of 20 nm thick is grown on the GaAs layer at 550°C in a MOVPE reactor. The GaAs layer capped with the GaN buffer layer is annealed in NH3 to 1000°C. Through this process, a porous GaN layer is formed beneath the GaN cap layer. An epitaxial GaN layer is grown on the GaN buffer layer at 1000°C in the MOVPE reactor. The epitaxial layer grown on the porous-GaN/Si(1 1 1) structure is found to have no cracks on the surface. In contrast, an epitaxial layer grown on the GaAs layer nitrated without a cap layer many cracks are found in the epilayer and the layer is sometimes peeled off from the substrate. It is found that the surface morphology of the GaN/porous-GaN/Si(1 1 1) sample is markedly improved by employing a 40 nm-thick interlayer grown at 800°C in addition to the above processes. A PL spectrum with a high intensity ratio between the excitonic emission and the deep yellow emission is obtained for the GaN/porous-GaN/Si(1 1 1) sample. E2 peak position in Raman scattering spectrum also shows a reduced stress for the GaN epilayers grown on the porous-GaN/Si(1 1 1).

Growth of GaN on Porous SiC by Molecular Beam Epitaxy

“…It was found in previous work that use of porous substrates can lead to significant strain relaxation in the film, at least in certain cases [20] [21].…”

“…This conclusion is, perhaps, not surprising when we carefully consider the geometry of the situation. The prior work which did observe a strain reduction was for GaN growth on porous GaN, employing a GaN buffer layer that was then etched to make it porous [20] [21]. It was found that the pores extended vertically down into the layer, i.e.…”

Improvement of the optical properties of GaN epilayers on Si(111): Impact of GaAs layer thickness on Si and pre‐growth strategy

“…GaAs has a lower yield strength than GaN, sapphire and Si, so cracking and plastic deformations or defects are more likely to occur in the GaAs layer rather than GaN epilayer [4]. In our past study, due to the formation of a porous GaN interlayer by novel nitridation of a 2 µm GaAs layer on Si(111), a crack free GaN epilayer was found to be grown over the interlayer and high intense excitonic emission intensity was obtained from the epilayer [5]. But in that study, the effect of GaAs layer thickness deposited on Si(111) and its nitridation impact on the optical properties of the GaN epilayers had not been focussed.…”

“…But in that study, the effect of GaAs layer thickness deposited on Si(111) and its nitridation impact on the optical properties of the GaN epilayers had not been focussed. Nitrogen has a certain diffusion length, so the novel nitridation [5] of different thickness GaAs layers and a study on the epilayer stress effect on cracking and optical properties are interesting issues. The near band edge luminescence intensity of GaN epilayers increases with decreasing stress and defects [3].…”

A comparative study on In‐doping effects for MOVPE GaN films on Si(111) and sapphire substrates

“…Therefore, crack generation becomes a serious problem in this case. In order to solve such problems, various growth techniques, ELOG [1], ABLOG [2], and porous interlayer formation [3] have been studied. A significant reduction of residual stress as well as improvement in the quality of epitaxial GaN grown on sapphire is attained by using isoelectronic In doping [4][5][6].…”