Growth and Characterization of AllnGaN/lnGaN Heterostructures
- PDF / 273,721 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 89 Downloads / 204 Views
here
is a paucity of successful activities in the growth of InxGal.xN with high values of x due to several difficulties that can be unique for this ternary alloy. The main problem is related to the weak In-N bond that necessitates a high nitrogen vapor pressure during the growth process. Plasmas generated by electron cyclotron resonance (ECR) in the molecular beam epitaxy (MBE) environment do not seem to produce enough of a nitrogen overpressure. For metalorganic chemical vapor deposition (MOCVD), the high temperature growth needed to crack NH3 will enhance the dissociation of In-N bonds. This paper will present the growth and characterization of In×Gaj.xN bulk films and InxGal.,N based heterostructures that have been deposited between -750 800 1C. There are apparent differences between the properties of the relatively thick (e.g., > -2000 A) InGaN films versus the thinner (e.g., < -200 A,) InGaN active layers of DHs. Although we have grown thick InxGal.xN films in our reactor with a value of x up to 0.40, the optical properties of these InxGalxN films with x > -0.30 begin to degrade rapidly with increasing x, and tend to have In metal segregated either on the surface or in the film, as detected by X-ray diffraction (XRD) analysis. Thinner lnxGal.xN films that are active layers of double heterostructures can be grown in our reactor with apparently higher values of x as determined by PL measurements. Emission in the yellow region of the visible spectrum with a good value of full width 341 Mat. Res. Soc. Symp. Proc. Vol. 423 0 1996 Materials Research Society
at half maximum (FWHM), has been observed. Most of the InGaN double heterostructures have been grown with AIGaN upper and lower cladding layers, but we have recently performed a few trials with AIInGaN cladding layers. EXPERIMENT Epitaxial growth of InxGal-xN was performed in a hybrid ALE/MOCVD growth system, that has been previously described2 . This hybrid ALE/MOCVD system was previously used for the epitaxial growth of In.Gaj_ N (0 < x < 0.27) by ALE 3 and of AIInGaN quaternary alloys by MOCVD". Source gases used were, trimethylgallium
0 (TMG, -10 °C), trimethylaluminum (TMA, + 18 C), ethyldimethylindium (EdMin, + 10 °C) and NH 3 ; N2 was used as the carrier gas. Basal plane sapphire, cleaved into - 1.5
cm x 1.5 cm squares, was used as substrate material. After solvent cleaning, substrates were loaded and annealed in N2 and NH3 for 15 minutes and 1 minute respectively. ALE growth of AIN/GaN buffer layers' was performed at 700 °C, while InGaN films were grown by MOCVD between 750 and 800 °C. The thick InGaN alloys were typically grown on GaN that was deposited by MOCVD at higher temperatures (900 - 950 1C). AIGaN grown at 950 °C was typically used as the cladding layers for the double heterostructures. RESULTS InGaN epitaxial layers have been grown with values of InN up to 40% in the ternary alloy. The full width at half maximum (FWHM) of the double crystal X-ray diffraction (DCXRD) data for these films is broad for high values of x, but is 3.4 3.3 3.2 3.1 3
Data Loading...
