Characterization of carbon-doped InSb diode grown by molecular beam epitaxy

Carbon-doped p-type InSb layers grown by solid source molecular beam epitaxy are characterized using a p+–n diode structure. Based on the combination of current–voltage, secondary ion mass spectroscopy and x-ray diffraction measurements, carbon is proven to be an effective p-type dopant for InSb with hole concentration reaching the range of 1019 cm−3. It is also proven that the use of the Hall effect to determine the hole concentration in the p-type InSb layer may be unreliable in cases where the leakage current in the p+–n junction is high. A thermal trap-assisted tunnelling model with two trap levels successfully explains the origin of leakage current mechanisms in the carbon-doped InSb samples. Good agreement between measured and calculated dc characteristics of the diodes at reverse bias up to −3 V from 30 to 120 K supports the validity of the current transport model.


Source:IOPscience

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Very long wavelength infrared focal plane arrays with 50% cutoff wavelength based on type-II InAs/GaSb superlattice

 A very long wavelength infrared(VLWIR) focal plane array based on InAs/GaSb type-II super-lattices is demonstrated on a GaSb substrate. A hetero-structure photodiode was grown with a 50% cut-off wavelength of 15.2   m, at 77 K. A 320×256 VLWIR focal plane array with this design was fabricated and characterized. The peak quantum efficiency without an antireflective coating was 25.74% at the reverse bias voltage of −20 mV, yielding a peak specific detectivity of   cm Hz  W⁻¹. The operability and the uniformity of response were 89% and 83.17%. The noise-equivalent temperature difference at 65 K exhibited a minimum at 21.4 mK, corresponding to an average value of 56.3 mK.

Source:IOPscience

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Photosensitization of InSb crystals by pulsed laser irradiation

The photosensitization of n-InSb single crystals after irradiation with nanosecond ruby laser pulses was studied. Based on a study of the photoconductivity spectra it is established that the surface recombination rate decreases in the samples subjected to subthreshold irradiation. The steady-state photoconductivity, non-equilibrium carrier lifetime and resistivity increases. Changes in the photo-electric properties of InSb crystals are attributed to the cleaning of the surface and to the gettering of electrically active point defects by extended growth defects. The role of laser-induced stress and shock waves in these processes is discussed. The method for changing the surface state and modifying the photo-electric parameters of InSb crystals and for improving the stability of their properties by means of pulsed laser irradiation is advanced.

Source:IOPscience

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Molecular beam epitaxy growth and characterization of InSb layers on GaAs substrates

The authors have investigated InSb layers grown heteroepitaxially on GaAs(100) substrates by molecular beam epitaxy (MBE). The dependence of electron mobilities on the MBE-growth conditions was investigated. The best room temperature mobility, 55000 cm2 V-1 s-1 for a 2 mu m thick layer, was obtained for a growth temperature of 420 degrees C with an antimony over indium ratio of 1.4. The 14.6% lattice mismatch between epilayer and substrate gives rise to threading dislocations and microtwins, as evidenced by transmission electron microscopy. The defects are shown to reduce the mobility for thin samples. One of the most interesting results of the work is the evidence of an electron accumulation layer at the InSb(100) surface. This result is obtained from temperature-dependent Hall measurements which exhibited two singularities in the carrier concentration versus temperature plot. Calculations of the Hall constant considering parallel conduction is successfully used to model this temperature dependence. The MBE-grown InSb layers are shown to have an unintentional acceptor background. The authors also investigated n-type doping using silicon. It is shown that the measured low temperature carrier concentrations and mobilities in undoped samples are considerably influenced by compensation effects.

Source:IOPscience

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