AVS 50th International Symposium
    Semiconductors Tuesday Sessions
       Session SC-TuM

Paper SC-TuM5
Nitrogen Incorporation and Strain Relaxation Mechanisms during Metalorganic Vapor Phase Epitaxy of GaAsN Layers on GaAs (001)

Tuesday, November 4, 2003, 9:40 am, Room 321/322

Session: Narrow Gap Semiconductors
Presenter: J.-N. Beaudry, École Polytechnique de Montréal, Canada
Authors: J.-N. Beaudry, École Polytechnique de Montréal, Canada
G. Bentoumi, Université de Montréal, Canada
S. Guillon, Bookham Technology, Canada
R. Leonelli, Université de Montréal, Canada
R.A. Masut, École Polytechnique de Montréal, Canada
P. Desjardins, École Polytechnique de Montréal, Canada
Correspondent: Click to Email
GaAs@sub 1-x@N@sub x@ epilayers (x @<=@ 0.04), nominally 200-nm-thick, were grown on GaAs (001) by metalorganic vapor-phase epitaxy using trimethylgallium, tertiarybutylarsine (TBAs), and dimethylhydrazine (DMHy). We carried out a systematic investigation of N incorporation as a function of the J@sub DMHy@/J@sub TBAs@ flow rate ratio for growth temperatures T@sub s@ varying from 500 to 650°C. Quantitative secondary ion mass spectrometry measurements indicate that N incorporation increases initially linearly with J@sub DMHy@ with a temperature-dependent incorporation probability that decreases from 0.0036 at 500°C to 0.0005 at 600°C to nearly zero at 650°C. The use of very large DMHy flow rates results in larger incorporation probabilities but lower growth rates. High resolution x-ray diffraction (HR-XRD) shows that the GaAs@sub 1-x@N@sub x@ lattice parameter decreases approximately linearly with increasing x up to about 0.02, with a strain coefficient corresponding to a linear interpolation between the lattice constants of GaAs and cubic GaN. At higher N fractions, the lattice parameter decreases more rapidly. Films with x up to approximately 0.02 are perfect single crystals with smooth interfaces as judged by HR-XRD and cross-sectional transmission electron microscopy (XTEM). Atomic force microscopy and cross-sectional imaging by transmission electron microscopy of a 230 nm thick layer with x = 0.0375 show that crack formation is the most important tensile strain relief mechanism although extrinsic stacking faults and misfit dislocations were also observed. Optical absorption and photoluminescence analyses reveal that higher crystalline quality and lower impurity concentrations were obtained for growth between 575 and 600°C.