MBE-Grown Hybrid Axial Core-Shell n-i-p GaAsSb Heterojunction Ensemble Nanowire-Based Near-Infrared Photodetectors up to 1.5 μm

In this paper, high-performance self-assisted molecular beam epitaxy (MBE)-grown conventional core-shell (C-S) n-i-p GaAsSb nanowires (NWs) and a novel hybrid axial C-S n-i-p GaAsSb ensemble NW-based near-infrared photodetector (NIRPD) on nonpatterned Si substrate are demonstrated. The conventional room-temperature (RT) C-S n-i-p GaAsSb NW with a high responsivity of 190 A/W and a higher detectivity of 1.1 × 1014 Jones at -1 V bias and wavelength of 1.1 μm is reported by optimizing the intrinsic region thickness and appropriately compensating the intrinsic p-type behavior with n-dopant Te. Furthermore, hybrid axial C-S n-i-p GaAsSb has been band-gap-engineered for wavelength up to 1.5 μm, exhibiting responsivity of 18 A/W and detectivity of 1.1 × 1013 Jones operating at RT. In this hybrid design, we have combined both axial and radial intrinsic (i-) segments of different Sb% compositions to enhance the photoabsorption in the NIR region; hence, the photogenerated current and also the high-band-gap axial i-region help to suppress the trap-assisted tunneling mechanism, which is found to be advantageous over conventional C-S NW architectures. In addition, high rectification ratio from current-voltage (I-V) measurements, suppression of low-frequency noise, lack of 1/f noise, a low corner frequency of ∼2.5 Hz beyond which there is the presence of only frequency-independent white noise from low-frequency noise (LFN) measurements, and bias- and frequency-dependent capacitance-voltage (C-V) measurements suggest the formation of a high-quality C-S junction in the hybrid structure. Thus, our findings reveal that the hybrid axial C-S NW architecture provides the flexibility of three-dimensional (3D) design, which offers an unprecedented prospect for expanding IRPD and other next-generation optoelectronic device applications.