Characterization of low Al content Al_xGa_1−xN epitaxial films grown by atmospheric‐pressure MOVPE

Abstract

Al x Ga 1Àx N epitaxial films grown on GaN/sapphire by atmospheric-pressure metalorganic vapor phase epitaxy (AP-MOVPE) using trimethylgallium (TMG) and trimethylaluminum (TMA) as group III precursors have been studied. Two groups of samples were grown. The aluminum (Al) solid composition of Al x Ga 1Àx N was varied in the range from 0.03 to 0.20 by changing the molar flow ratio [TMA/(TMA þ TMG)]. The effect of TMA flow rate, respectively, TMG flow rate, on the growth rate, and Al solid composition is discussed. The structural properties of the alloys have been investigated by high-resolution X-ray diffraction (HRXRD). The optical properties of these samples were investigated by photoluminescence (PL). It is found that on increasing Al solid composition, via an increase of the TMA flow rate, the structural quality is deteriorated and the growth efficiency decreases. On the other hand, when the TMG flow rate is reduced, a decrease of the full width at half-maximum (FWHM) is observed with Al content.

Bandgap and refractive index estimates of InAlN and related nitrides across their full composition ranges

“…The parameters A ( x ) and B ( x ) were obtained by fitting experimental values across the composition range and managed to deal effectively with AlGaN alloys 63 , 64 . However, based on our knowledge, there are currently no such systematic values for InAlN and InGaN materials.…”

Investigations of in situ reflectance of GaN layers grown by MOVPE on GaAs (0 0 1)

“…Their potential as a nondestructive, real-time monitoring tool present a considerable support to be used during the growth process. Among these tools, lasers reflectometry is the most successfully used in MOVPE, due to its easy installation [41,42]. This technique gives information's on both growth rate and surface roughness during growth [43][44][45][46].…”

Modification of the Surface Properties of AlxGa1–xN Substrates with Gradient Aluminum Composition Using Wet Chemical Treatments

“…The Al content, x , of Al x Ga 1– x N films has a strong influence on the properties of the material. Many reports are available on the dependence of the electrical and optical properties of Al x Ga 1– x N on the Al content of the film. − The Al content is also known to affect the dislocation density of Al x Ga 1– x N films grown heteroepitaxially on various substrates because of different levels of strain induced by lattice and thermal expansion coefficient mismatch. − Surface defect type and density also vary for variable Al content, which affects the roughness, electron affinity, and morphology of the surface. ,, We aimed to use these varying surface properties to selectively modify the surface of an Al x Ga 1– x N gradient film with composition x varying between 0.173 and 0.220 by using wet etching and chemical functionalization approaches to form chemical gradients.…”