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Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures (1996)

Chin, Albert ; Chen, W. J. ; Ganikhanov, F. ; [et al.]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 69 (1996), S. 397-399

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ISSN: 1077-3118

Source: AIP Digital Archive

Topics: Physics

Notes: 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 A(ring) in size) whose grain boundaries provide effective carrier traps and recombination centers. © 1996 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.118073

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Ultrafast response of multi-energy proton-bombarded GaAs photoconductors (2000)

Lin, G.-R. ; Pan, C.-L.

Springer

Optical and quantum electronics 32 (2000), S. 553-571

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ISSN: 1572-817X

Keywords: carrier lifetime ; electro-optic sampling ; photoconductor ; proton-bombarded GaAs ; THz radiation

Source: Springer Online Journal Archives 1860-2000

Topics: Electrical Engineering, Measurement and Control Technology , Physics

Notes: Abstract We have investigated the ultrafast optical and optoelectronic characteristics of multi-energy proton-bombarded GaAs (GaAs:H+) material and devices in some detail. Photo-excited carrier lifetimes of GaAs:H+ were observed to be as low as 350 ± 50 fs. Photoconductive switches (PCS) fabricated on GaAs:H+ were found to exhibit lower dark currents (15 nA at a bias of 10 V) and higher breakdown voltage (〉 100 kV/cm) than PCS's fabricated on semi-insulating (S.I.) GaAs. The temporal response of the GaAs:H+ PCS was about 2 ps at full-wave half minimum. Optically excited terahertz (THz) radiation from GaAs:H+ was reported for the first time to our knowledge. The temporal response and spectral bandwidth of the emitted THz radiation were 0.7 ps and 1.25 THz, respectively. The field strength of the THz signal was about 20 mV/cm. From the THz data, we are able to deduce that the effective carrier mobility of GaAs:H+ was less than 1 cm2/V-sec.