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Midinfrared (6.3 and 8.4 mum) InxGa 1-xAs/In0.52Al0.24Ga 0.24As quantum wire infrared photodetectors (QRIPs) grown on semi-insulating (001) on-axis InP substrates via solid-source molecular beam epitaxy (MBE) have been fabricated and characterized. The quantum wires (QWRs) were formed using an in situ on-step strain-induced lateral-layer ordering (SILO) method. The layered (GaAs)1.80/(InAs)2.35 short-period superlattice (SPS) forms QWRs, with a high density of ∼1 x 10 6 cm-1, via the SILO process. The QWR characteristics were confirmed using polarized photoluminescence (PPL) and cross-sectional transmission electron microscopic (XTEM) images in structures incorporated with different number of SPS pairs and barrier material. The multiple-layer QRIP structure was proven to be strained-balanced by examining the high-resolution X-ray diffraction (HRXRD) spectra. Excellent layer-to-layer QWR uniformity and optical quality in QRIP structures were achieved with ease. The preliminarily optimized QRIP design parameters were determined by background current-voltage characterization and a theoretical simulation to be 6 SPS pairs, a 500 A In0.52Al0.24Ga0.24As barrier, and a constant SPS monolayer ratio of 1.80/2.35 along with an appropriate doping profile. The QRIP device fabricated using these optimal parameters showed a detection wavelength of 8.4 mum and a peak detectivity of 8.97 x 109 cmHz1/2/W at 10 K under a normal-incident scheme. This device displayed characteristics of low dark current and a correspondingly low responsivity. Another QRIP device with 10 SPS pairs demonstrated three photocarrier transitions, as theoretically predicted, with a highest detectivity of 3.13 x 109 cmHz1/2/W at 6.3 mum. A higher detectivity for the device with 6 SPS pairs in QWRs and a single optical transition resulted from a better QRIP design. The performance of both devices was found to be limited by the current blocking layer formed at the leading edge of the QWR region and could be improved by modifying the layer composition.
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