Study on the InAs-based materials and devices grown by a molecular beam epitaxy system
Date Issued
2012
Date
2012
Author(s)
Wu, Chen-Jun
Abstract
We determined the unstrained conduction band and valence band edge energies of InAs1-xSbx (0.05 < x < 0.13) by fitting the photoluminescence (PL) peak energy of InAsSb/InAs0.67P0.23Sb0.10 multiple quantum wells (QWs) that was measured in the temperature range 10 – 300 K. The results reveal that the QWs exhibit type-I band alignment. Furthermore, the valence band accounts for 65% of the energy gap bowing of InAsSb. We propose a valence-band anticrossing (VBAC) model to explain the bowing of the valence band in InAsSb. Moreover, the spin-orbit splitting energy of InAsSb calculated by our VBAC model fits well with the experimental results reported in the previous studies. From the Arrhenius plot of the PL integrated intensity, two activation energies of each sample are retrieved. We calculated the energy of electrons escape from the conduction band confinement and the electron hole pairs escape from the QW confinement based on the InAsSb/InAs0.67P0.23Sb0.10 band alignment. One of the composition dependence of the activation energies is close to the one of the carriers escape energy. Therefore, we attributed the activation energies to the carrier bipolar emission from the QW confinement. The other activation energy could be due to the electron escape from the MQW.
We used the high energy gap and lattice matched InAsPSb as the window layer and studied the InAsPSb/InAs hetero-junction PIN photodetectors. The best responsivity of a 1.5 μm i-layer sample is 1.64 A/W at the wavelength of 3.0 μm. If the 65% transmittance of the surface of the devices is considered, the internal quantum efficiency can be as high as 100%. And a peak of detectivity of 5.4x109 cm-Hz1/2/W was obtained at the wavelength of 3.0 μm.
We performed reciprocal space mapping (RSM) and extended X-ray absorption fine structure (EXAFS) to investigate the lattice structure of 1-μm-thick InP0.52Sb0.48 and InAsPSb grown on GaAs substrates. The thickness of the epilayer is much larger than the critical thickness. The RSM data reveals that the average vertical to horizontal lattice constant ratio (az/axy) of the InAsPSb samples increases as the As mole fraction decreases. We used a valence force field model to calculate the distortion energy and bond lengths of InPSb and InAsPSb supercells with different az/axy ratio. The calculated bond lengths are in good agreement with the results of EXAFS. The bond lengths are close to those in corresponding end-point binaries. The distortion energy of the InAsPSb sample increases as the As mole fraction decreases. Therefore, we attributed the strain sustained in the alloys to work hardening due to the strongly distorted bonds.
Subjects
molecular beam epitaxy
InAsPSb
InPSb
valence band anticrossing model
thermal quenching
photodetector
valence force field model
Type
thesis
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