Ensemble GaAsSb/GaAs axial configured nanowire-based separate absorption, charge, and multiplication avalanche near-infrared photodetectors

Abstract

In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented. Our device exhibits a low breakdown voltage (V _BR) of ∼ -10 ± 2.5 V under dark, photocurrent gain (M) varying from 20 in linear mode to avalanche gain of 700 at V _BR at a 1.064 μm wavelength. Positive temperature dependence of breakdown voltage ∼ 12.6 mV K^-1 further affirms avalanche breakdown as the gain mechanism in our SACM NW APDs. Capacitance-voltage (C-V) and temperature-dependent noise characteristics also validated punch-through voltage ascertained from I-V measurements, and avalanche being the dominant gain mechanism in the APDs. The ensemble SACM NW APD device demonstrated a broad spectral room temperature response with a cut-off wavelength of ∼1.2 μm with a responsivity of ∼0.17-0.38 A W^-1 at -3 V. This work offers a potential pathway toward realizing tunable nanowire-based avalanche photodetectors compatible with traditional Si technology.

Fig. 1. Schematic process of NW APD device fabrication following epitaxial growth by MBE.

Fig. 2. Single SACM axial NW APD (a) schematic, (b) band diagram under zero and reverse bias operations, and (c) E-field distribution plot at −10 V.

Fig. 3. High-density as-grown ensemble axial SACM NW APDs (a) SEM image of NW APD growth on n-Si<111> (inset: single NW SACM APD core), and (b) 4K PL spectra.

Fig. 4. Ensemble SACM axial NW APD device (a) I–V characteristics at RT under dark and light, (b) gain under illumination with increasing reverse bias, and (c) temperature dependence of V_BR from 77 K to 350 K using I–V–T characteristics under dark.

Fig. 5. Ensemble SACM axial NW APD device: (a) spectral response at punch through voltage ∼ −3 V, with an illumination power of ∼5 mW, and (b) laser excitation power dependence at RT for different reverse bias.

Fig. 6. Ensemble SACM axial NW APD device (a) RT capacitance versus reverse bias characteristics under illumination, and (b) capacitance vs. frequency dependence under dark.

Fig. 7. Ensemble SACM axial NW APD device noise characteristics: (a) under illumination at RT with varying reverse bias, and (b) under dark at −5 V for 77 K and RT.