MBE-grown AlN-on-Si with improved crystalline quality by using silicon-on-insulator substrates

Abstract

This paper reports on AlN epilayers with improved crystalline quality grown on silicon-on-insulators (SOIs) by plasma-assisted molecular beam epitaxy (PAMBE). The influences of the substrate on threading dislocation (TD) and surface morphology have been investigated. Two sets of wafers were grown on Si and SOI substrates with the same optimized growth parameters. An atomically smooth AlN epilayer was realized on an SOI substrate with reduced TD density compared to that on Si. This result is attributed to the stress release effect due to the lattice distortion in the top silicon layer of the SOI substrate.

Molecular Beam Epitaxial Growth of AlN Thin Films on Si through Exploiting Low Al Adatom Migration and the Nitrogen-Rich Environment on a Nanowire Template

“…Hitherto, with the aim of obtaining high-quality AlN on Si, different approaches have been developed. These include applying the NH 3 pulsed-flow growth mode in a MOCVD chamber, 14 using silicon-on-insulator (SOI) wafers, 26 employing Si substrates with different orientations, 28 and exploiting the lateral epitaxial overgrowth (LEO) on patterned substrates. 12,27,30−32 Indeed, high-quality AlN thin films have been achieved on patterned Si.…”

“…In the past, various techniques have been used for the growth of AlN on Si, including molecular beam epitaxy (MBE), metal–organic chemical vapor deposition (MOCVD) and/or metal-organic vapor phase epitaxy (MOVPE), and pulsed laser deposition (PLD). ,− However, it remains challenging today to grow high-quality AlN thin films on Si, due to the large thermal and lattice mismatches between AlN and Si. Different from the growth of GaN on Si, wherein the tensile strain can be compensated by using AlN and/or AlGaN buffer layers that introduce compressive strain, for the growth of AlN on Si, there are no such strain compensation buffer layers due to the unavailability of a material that can be grown epitaxially with a lattice constant smaller than that of AlN.…”

“…Hitherto, with the aim of obtaining high-quality AlN on Si, different approaches have been developed. These include applying the NH 3 pulsed-flow growth mode in a MOCVD chamber, using silicon-on-insulator (SOI) wafers, employing Si substrates with different orientations, and exploiting the lateral epitaxial overgrowth (LEO) on patterned substrates. ,,− Indeed, high-quality AlN thin films have been achieved on patterned Si. − ,,, In spite of the progress, the growth on patterned Si remains a costly process. Lithography and etching processes, which are required for the wafer patterning, add additional time and dollar cost.…”

Molecular Beam Epitaxy of AlGaN Epilayers on Si for Vertical Deep Ultraviolet Light-Emitting Diodes

“…The main approaches, hitherto, used to improve the quality of AlGaN epilayers on Si include using epitaxial lateral overgrowth (ELO)-AlN buffer layers, AlGaN/AlN superlattices, and graded AlGaN buffer layers. [9][10][11][12][13][14][15][16][17] Even with these efforts, there are only limited reports of AlGaN deep UV LEDs on Si. 8,[18][19][20][21][22] Furthermore, the shortest device operation wavelength reported so far has been limited to 257 nm.…”