Gas source molecular beam epitaxy of high quality AlxGa1−xN (0⩽x⩽1) on Si(111)

Abstract

Layers of AlxGa1−xN, with 0⩽x⩽1, were grown on Si(111) substrates by gas source molecular beam epitaxy with ammonia. We show that the initial formation of the Si–N–Al interlayer between the Si substrate and the AlN layer, at a growth temperature of 1130–1190 K, results in very rapid transition to two-dimensional growth mode of AlN. The transition is essential for subsequent growth of high quality GaN, AlxGa1−xN, and AlGaN/GaN superlattices. The undoped GaN layers have a background electron concentration of (2–3)×1016 cm−3 and mobility up to (800±100) cm2/V s, for film thickness ∼2 μm. The lowest electron concentration in AlxGa1−xN, with 0.2<x<0.6, was ∼(2–3)×1016 cm−3 for 0.5–0.7-μm-thick film. Cathodoluminescence and optical reflectance spectroscopy were used to study optical properties of these AlxGa1−xN layers. We found that the band gap dependence on composition can be described as Eg(x)=3.42+1.21x+1.5x2. p–n junctions have been formed on crack-free layers of GaN with the use of Mg dopant. Light emitting diodes with peak emission wavelength at 3.23 eV have been demonstrated.

Formation of AlN and GaN nanocolumns on Si(111) using molecular beam epitaxy with ammonia as a nitrogen source

“…The lower onset temperature for AlN protrusion formation is consistent with previous observations that ammonia decomposed more readily on an AlN surface than on a GaN surface. [6] The platelets were so large that a reduction in surface species diffusion length is unlikely to explain their formation. No new material phases were observed either by XRD or energy dispersive X-ray spectroscopy for the platelet structures.…”

“…2 and 3 were from 8 to 9 x 10 -6 Pa, which yielded a growth rate of 0.03 nm/s. As in previous work, [5,6] the AlN layers were initiated with a thin layer (0.3 to 0.5 nm) of pure Al before the surface was exposed to ammonia and AlN growth began.…”

AlGaN‐based heterostructures grown on 4 inch Si(111) by MOVPE

“…However, there are few reports on AlGaN growth on silicon substrates [6][7][8], partially due to the extra difficulty resulting from the large thermal mismatch between AlGaN and silicon. In our previous work [9,10], we demonstrated crack-free GaN layers up to 3 µm on 4 inch silicon(111) substrates using step-graded AlGaN intermediate layers.…”

AlGaN-Based Photodetectors Grown by Gas Source Molecular Beam Epitaxy with Ammonia

“…GaN layers and p-n junctions can be grown by gas source MBE (GSMBE) with ammonia [3] under temperatures sufficiently high [4] to achieve excellent optical and electrical properties. Another advantage of GSMBE with ammonia is that the p-type conductivity can be obtained in as-grown GaN : Mg and Al x Ga 1--x N : Mg (x < 0.1) [5]. We have also shown recently that layers and structures based on Al x Ga 1--x N, grown on Si or sapphire substrates by GSMBE with ammonia, are free of cracks [6].…”