Growth of InAsPSb Quaternary Alloy by Gas Source Molecular Beam Epitaxy
Date Issued
2009
Date
2009
Author(s)
Tsai, Gene
Abstract
Among III-V compound semiconductors, InAsSb material system has the lowestandgap energy ranging from 0.417 eV (InAs) to 0.235 eV (InSb) and is the best activeayer candidate for IR gas detectors. In this study, series of InAsSb alloy samples wererown using solid source molecular beam epitaxy on InAs substrates to investigate theirurface morphology, structural and optical characteristics. Increasing growthemperature enhances the As incorporation and leads to the decreasing of Sb moleraction. Under microscope investigation, XRD FWHM broadens and relaxationnduced crosshatch begins to appear on epilayer surface with increasing Sboncentration. Photoluminescence (PL) measurement was also taken to acquire allamples’ bandgap energy and qualitatively compare each sample’s opticalharacteristics. Transition energies of above mentioned samples are within the range of.2~0.4 eV (3~5 um). For InAsSb/InAs multiple quantum wells grown at differentubstrate temperature, sample exhibits better optical quality with growth temperaturelose to 450oC and 4 K photoluminescence result shows that the band alignment wasetermined to be staggered type-II. From samples with the Sb mole fraction rangingrom 0.06 to 0.13, it was found that both the conduction and valence bands of InAsSblloy exhibit some bowing by comparing the emission peak energies with a transitionnergy calculation. The bowing parameters were determined to be in the ratio of 4:6.or a sample with Sb composition ~0.12 in the quantum well the photoluminescencemission band covers the CO2 absorption peak making it suitable for use in sources forO2 detection.nPSb ternary sample were also successfully grown on InAs substrate which weelieve that it is the first demonstration of MBE grown single phase InPSb bulk layer onnAs. The XRD FWHM of InPSb epilayer signal is only 65arcsec. Substrate effect andhase separation were observed for InPSb grown on InP and GaAs substrates. Halleasurements shows that Be and Si can be p-type and n-type dopants for InPSbaterial respectively.or InAsPSb quaternary, bandgap energies of quaternary as well as miscibilityap using strictly regular solution approximation are calculated. For InAs latticeatched InAsPSb samples grown at 470oC, the As composition limit is 0.39. Rougherurface morphology can be seen as the arsenic composition in quaternary bulkncreasing. Near band edge photoluminescence emission is observed for high As moleraction sample while 223 meV of deviation between PL energy and calculated bandgapnergy for InAs0.04P0.67Sb0.29. Two photoluminescence bands are resolved. Theaussian-like line shape is attributed to be the result of deep-level defects which can bellustrated by configuration coordination model. The deep levels are possibly due toacancy-impurity complexes that are composed of a substitutional carbon and an Inacancy, i.e., a VIn-CAs or VIn-CIn complex. The other band located lat low energy sidehose peak redshifts and intensity decreases as temperature increasing is ascribed to thearrier recombination in the tail states.nAsPSb p-i-n photodetectors were made to be operated in room temperaturesing gas source molecular beam epitaxy. The surface illuminated photodetector with aesa structure were fabricated by a conventional device process. The detectableavelength ranges from 1um to near 3 um with peak responsivity equal to 0.3 A/Wocated at 2.6 um. The Johnson noise limited detectivity of 1.7×109 cmHz1/2/W isomparable with PbSe detector operates at 77 K and outperforms that at 300 K.
Subjects
Mid-Infrared
Molecular Beam Epitaxy
InAsSb
InPSb
InAsPSb
III-V semiconductor
Type
thesis
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