Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures

Albert Chin*, W. J. Chen, F. Ganikhanov, G. R. Lin, Jia Min Shieh, Ci Ling Pan, K. C. Hsieh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Cross-sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70°C. A columnar polycrystalline GaAs is observed for samples grown at 160°C while it appears amorphous for samples grown at temperatures below 120°C. The successful growth of amorphous (Ga,As) at 70°C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as-grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (∼500 Å in size) whose grain boundaries provide effective carrier traps and recombination centers.

Original languageEnglish
Pages (from-to)397-399
Number of pages3
JournalApplied Physics Letters
Issue number3
StatePublished - 15 Jul 1996

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