HARPIA-TG is a transient grating spectrometer for the measurement of carrier diffusion and lifetime. Measurements are based on the laser-induced transient grating (LITG) technique. This method enables simultaneous observation of non-equilibrium carrier recombination and diffusion by all‑optical means.

HARPIA-TG allows the characterization of electrically non‑conductive or non-fluorescent samples. It is suitable for semiconductors materials and derivatives, e.g., silicon carbide (SiC), gallium nitride (GaN), perovskites, organic and inorganic solar cells, quantum dots, and even complex nanostructures such as quantum wells.

Coupled with CARBIDE or PHAROS laser with integrated optical parametric amplifier (I-OPA), the compact system is fully automated and computer-controlled via advanced measurement and analysis software. Thus, the user only needs to put the sample in the holder and start the measurement to obtain the diffusion coefficient in a matter of minutes.

Applications

Transient grating spectroscopy
Single-wavelength transient absorption

Specifications

Model	HARPIA-TG
Grating recording wavelength ¹⁾	340 – 560 nm
Probe wavelength ²⁾	1030 nm
Grating period ³⁾	1.15 – 15 μm
Pulse duration	< 290 fs
Delay range	Up to 8 ns

Extendable to long-wave VIS/NIR. Contact sales@lightcon.com for details.
SH (515 nm) or OPA-based probe is available upon request. Contact sales@lightcon.com for details.
Depends on the excitation wavelength.

Measurement ranges

Model	HARPIA-TG
Diffusion coefficient	0.1 – 50 cm²/s
Carrier lifetime	1 ps – 80 ns

Dimensions

Model	HARPIA-TG
Physical dimensions (L × W × H)	730 × 420 × 188 mm

Performance

The graphs below indicate the carrier diffusion coefficient, diffusion length, and lifetime of GaN at the back and at the front of the layer as a function of fluence. The thicker the GaN, the better the quality of the grown layer due to better coalescence. It is evidenced by the lower diffusivity and shorter lifetimes that indicate poor structural quality and higher defect density at the interface between the sapphire substrate and GaN.

Measurements were performed using HARPIA-TG combined with CARBIDE-CB5 laser and I-OPA. Measurement conditions: 60 kHz, 355 nm pump wavelength, 1030 nm probe wavelength.

Diffusion coefficient of GaN as a function of fluence

Carrier lifetime of GaN as a function of fluence

Diffusion length of GaN as a function of fluence

Images & Drawings

Principal scheme of HARPIA-TG

Drawing of HARPIA-TG

Recommended layout with CARBIDE-CB5 and I-OPA

HARPIA-TG dedicated software

HARPIA-TG offers a dedicated software that enables fully automated selection of pump and probe parameters and grating period, thus, making the measurements of diffusion coefficient and carrier lifetime as simple as possible.