Cross-sectional Kelvin probe force microscopy on III-V epitaxial multilayer stacks: challenges and perspectives.

Multilayer III-V-based solar cells are complex devices consisting of many layers and interfaces. The study and the comprehension of the mechanisms that take place at the interfaces is crucial for efficiency improvement. In this work, we apply frequency-modulated Kelvin probe force microscopy under ambient conditions to investigate the capability of this technique for the analysis of an InP/GaInAs(P) multilayer stack. KPFM reveals a strong dependence on the local doping concentration, allowing for the detection of the surface potential of layers with a resolution as low as 20 nm. The analysis of the surface potential allowed for the identification of space charge regions and, thus, the presence of several junctions along the stack. Furthermore, a contrast enhancement in the surface potential image was observed when KPFM was performed under illumination, which is analysed in terms of the reduction of surface band bending induced by surface defects by photogenerated carrier distributions. The analysis of the KPFM data was assisted by means of theoretical modelling simulating the energy bands profile and KPFM measurements.

Low-κ, narrow linewidth III-V-on-SOI distributed feedback lasers with backside sampled Bragg gratings.

We demonstrate a heterogeneously integrated III-V-on-SOI distributed feedback laser with a low grating strength (κ < 40 cm-1) and a narrow linewidth of Δν = 118 kHz. The laser operates single mode with a side-mode suppression ratio over 45 dB, provides a single-sided waveguide-coupled output power of 22 mW (13.4 dBm) and has a wall-plug efficiency of 17%. The dynamic characteristics were also evaluated, obtaining an intrinsic 3 dB modulation bandwidth of 14 GHz and a photon lifetime of 8 ps. Large-signal intensity modulation using a 231-1 PRBS pattern length revealed open eye diagrams up to 25 Gb/s and a penalty on the dynamic extinction ratio lower than 1 dB after transmission over a 2 km standard single mode optical fiber.

Micro-transfer-printed narrow-linewidth III-V-on-Si double laser structure with a combined 110 nm tuning range.

In this work, we demonstrate for the first time a narrow-linewidth III-V-on-Si double laser structure with more than a 110 nm wavelength tuning range realized using micro-transfer printing (µTP) technology. Two types of pre-fabricated III-V semiconductor optical amplifiers (SOAs) with a photoluminescence (PL) peak around 1500 nm and 1550 nm are micro-transfer printed on two silicon laser cavities. The laser cavities are fabricated in imec's silicon photonics (SiPh) pilot line on 200 mm silicon-on-insulator (SOI) wafers with a 400 nm thick silicon device layer. By combining the outputs of the two laser cavities on chip, wavelength tunability over S+C+L-bands is achieved.

Rochelle Salt-Based Ferroelectric and Piezoelectric Composite Produced with Simple Additive Manufacturing Techniques.

More than one century ago, piezoelectricity and ferroelectricity were discovered using Rochelle salt crystals. Today, modern societies are invited to switch to a resilient and circular economic model. In this context, this work proposes a method to manufacture piezoelectric devices made from agro-resources such as tartaric acid and polylactide, thereby significantly reducing the energy budget without requiring any sophisticated equipment. These piezoelectric devices are manufactured by liquid-phase epitaxy-grown Rochelle salt (RS) crystals in a 3D-printed poly(Lactic acid) (PLA) matrix, which is an artificial squared mesh which mimics anatomy of natural wood. This composite material can easily be produced in any fablab with renewable materials and at low processing temperatures, which reduces the total energy consumed. Manufactured biodegradable samples are fully recyclable and have good piezoelectric properties without any poling step. The measured piezoelectric coefficients of manufactured samples are higher than many piezoelectric polymers such as PVDF-TrFE.