Competition between sub-bandgap linear detection and degenerate two-photon absorption in gallium arsenide photodiodes

Abstract

This letter is on the response of gallium arsenide p-i-n diodes to sub-bandgap photons (1.55 μm). We investigate the various regimes of sub-bandgap operation by using different light sources delivering pulses ranging from nanosecond to microsecond durations. We evidence two regimes : a regime of degenerate two-photon absorption, with a clear quadratic dependence with respect to the incident flux, and a sub-bandgap, temperature dependant linear regime, that drives photocurrent generation at lower power densities. Both processes are associated to a very low quantum efficiency, around 10-8. We then determine absorption coefficients as well as trap densities, thanks to a model involving a photo-assisted Shockley Read Hall effect.

Methodology of optimisation for a nanostructured two-photon absorption photodetector

“…The intensity map on Figure 1.c illustrates the capability of the nanostructure to concentrate and colocalise the intensities I p and I s , thus increasing the TPA by a gain G = 120 for the optimal optical configuration (a collimated TE polarised 3.39 µm signal at normal incidence and a collimated TE-polarised pump at 1.06 µm pump with an angle of incidence of 11.83 • ). However, other pump related subbandgap processes have been shown to compete with NDTPA [29,30,31], leading to a higher background current and thus a lower SNR especially for low signal intensity.…”

Optimised bi-resonant nanostructured diode for infrared photodetection through non degenerate two-photon absorption

“…This phenomenon has been studied in several materials (silicium, gallium arsenide) and is explained as a photo-assisted Shockley-Read-Hall (PASRH) process. 6,7 The second term is the degenerate two-photon absorption of the pump. 3 The last one comes from the non-degenerate E-Mail : baptiste.fix@onera.fr two-photon absorption (NDTPA), which is the absorption of pump and signal photon.…”

Mid-infrared two-photon absorption in an extended-wavelength InGaAs photodetector

“…A theoretical value for the nonlinear coefficient of extendedwavelength In 0.81 Ga 0. 19 As can be predicted using the theoretical scaling law of β (2) with E −3 g given by 9,10,14…”

“…In this work we study TPA in a commercial photodiode (PD) based on extended wavelength In 0.81 Ga 0. 19 As, having a threshold for one-photon absorption at 2.8 µm -much larger than that of standard In 0.53 Ga 0.47 As (1.8 µm) lattice-matched to InP. This may potentially enable broadband TPA at wavelengths between 2.8 and 5.6 µm.…”

“…The PD is a commercial extended-wavelength In 0.81 Ga 0. 19 As photovoltaic detector (Teledyne Judson Technologies) operating at room temperature and without applied bias, having an active window size of 250 µm diameter. The 50% responsivity cutoff wavelength of the PD is 2.6 µm.…”