Trap-dependent current suppression of optically excited III-V nanowires at cryogenic temperatures

Abstract

The advancement of quantum technology networks necessitates high-speed, low-thermal load, and minimal-noise communication links between cryogenic and room-temperature components. At the heart of modern telecommunication, lay optical interconnects allowing for large data transfer capabilities via optical fibers. However, cryogenic photonic technologies remain largely unexplored and require a detailed understanding of material behavior and defect dynamics at low temperatures. In this work, we present the first comprehensive study of integrated III-V heterostructures operating at cryogenic temperatures down to 5K. Using an integrated n-InP/i-InGaAs/p-InP/p-InGaAs stack monolithically grown on silicon, we identify a temperature-dependent current-lowering mechanism arising from trap states becoming increasingly active below 140K. We demonstrate for the first time that these traps can be equivalently excited and controlled through either thermal or optical energy, revealing a dual modulation mechanism. These findings provide new insights into carrier transport and defect behavior in III-V heterostructures at cryogenic temperatures, advancing the field of cryogenic photonics and offering a non-destructive approach for identifying and characterizing material impurities in integrated quantum and optoelectronic devices.

Figures (6)

• Figure 1: Proposed hybrid scheme using cryogenic photonic integrated circuits (cryoPIC) for quantum computing. Information is communicated between the distributed control electronics and the room temperature controller via optical fibers. Modulated light is coupled to the cryoPIC using grating couplers and directed to the electo-optic device via integrated silicon ridge waveguides.
• Figure 2: (a) Experimental set-up for cryogenic characterization and study of devices. Liquid helium cooled cryostat (chamber picture in the inset) enables cooling down to 4K. (b) SEM of fabricated waveguide-coupled III-V nanowire with integrated half-zone plate reflector to optimize optical absorption. (c) EDX image of device, highlighting local distribution of P, As and Ga compositions. (d) TEM images of the fabricated heterostructures for $<100>$ SOI orientation.
• Figure 3: (a) Dark-current IV curves at temperatures between 300 to 5K. (b) Ideality (red) and saturation current (blue) data extracted from dark-current measurement vs temperature. The data points were fitted using the Levine model for the ideality factor and a quadratic fit for the saturation current. (c) Photocurrent IV characterization at 10K (left) and 280K (right) at varying laser powers at 1550nm wavelength. All the IV curves are plotted in absolute value of the current. (d) Responsivity of nanowire vs Temperature for different wavelengths.
• Figure 4: (a) Current vs Temperature plot for varying low optical excitation highlighting the current lowering up to 140K. Measurements were done at 1550nm with varying optical powers. (b) Richardson plot extrapolated from experimental data with corresponding activation energies at different temperature regimes. (c)-(d) Schematic explaining the fabricated III-V heterostructures behavior at different temperature regimes, highlighting the presence of shallow ($\mathrm{E_1}$) and deep ($\mathrm{E_2}$) defects that progressively get excited by thermal noise.
• Figure 5: (a) Current vs laser power percentage at 1550nm for different temperatures. The current for each temperature is normalized over the dark current and the dotted black line represents unity. (b) Threshold energy (corresponding to optical energy of the current lowering minima) vs temperature. (c) Current vs laser power percentage at 30K for different wavelengths. The current at each wavelength is normalized by the dark current at 30K. The unity line is represented by the black dashed line. (d) Threshold energy vs Wavelength at 30K with linear fit of the data. (e) Bar plot of Energy vs Temperature. Thermal energy (blue bars) and optical threshold energy (red bars) are summed showing a total energy equivalent to thermal energy at 140K (black dashed line).