Near-Infrared Photoluminescence Measurement System
MNIRPL-532
Near-Infrared Photoluminescence Measurement System MNIRPL-532
 
Photoluminescence (PL) is a technique for non-destructively evaluating the electronic states, defects, and impurity levels in a material. It works by irradiating the material with light to excite electrons, then spectrally resolving and detecting the light (luminescence) emitted as those excited electrons return to the ground state. By analyzing the energy position, intensity, and width of the emission spectrum, the band structure, lattice perfection, trace impurity distribution, and other properties of the material can be determined.

This system uses a 532 nm laser as the excitation light source and is designed mainly to measure emission in the near-infrared region. It is well suited to characterizing devices that emit in the near-infrared region and photodetectors that operate in the near-infrared wavelength range.

Measurements can provide information such as:
  • Calculation of band gap energy (for small- to medium-band-gap materials)
  • Detection of emission from bound and free excitons
  • Estimation of donor and acceptor impurity concentrations
  • Non-destructive detection of lattice and interface defects
  • Evaluation of epitaxial growth processes
Because evaluation is non-contact and non-destructive, it is an effective characterization tool across a wide range of stages, from materials development to mass-production inspection and reliability evaluation.

■Specifications
Excitation wavelength 532 nm
Measurement wavelength range 1100 nm to 1900 nm
Excitation wavelength cleanup Prism dispersion method
Sample holder Sample size: 2 mm square to φ50.8 mm
Sample positioning mechanism X: ±30 mm　Y: ±30 mm　Z: ±6.5 mm

*Specifications and appearance are subject to change without notice for improvement.

■Basic Principle of Photoluminescence (PL)

Photoluminescence (PL) is an optical technique in which a material is irradiated with high-energy light (excitation light), exciting electrons in the valence band to higher energy levels such as the conduction band, and the light (photons) emitted as they return to the ground level is detected and analyzed. This phenomenon is widely used to evaluate electronic states and diagnose material quality, mainly in semiconductor materials and phosphors.

As shown in the figure, electrons at the ground level (in most cases, the top of the valence band) absorb the energy of the externally applied excitation light and are excited to a higher energy level (typically the conduction band). This creates electron-hole pairs.

Diagram of the basic principle

However, excited electrons do not necessarily recombine immediately and undergo radiative transitions. In many cases, they pass through relaxation mechanisms such as those shown below before recombining.

  • Non-radiative relaxation: A process in which excited electrons lose energy as heat through interaction with lattice vibrations (phonons). No photons are emitted in this process.
  • Trapping by defect or impurity levels: Electrons may be temporarily captured at intermediate levels formed by defects or impurities in the crystal lattice, and when they return from there to the ground level, light with energy lower than the band gap may be emitted.

Because of these processes, the emission spectrum observed in PL measurements does not necessarily directly reflect the energy difference between the incident photons and the band gap, but is influenced by the various relaxation pathways within the material.

PL is a highly sensitive evaluation technique that can be applied to samples without contact or damage. In addition to analyzing band structures and energy levels, it can comprehensively provide information on crystallinity, defect density, impurity distribution, and more. It is regarded as an especially important technique for materials development and quality control of semiconductor devices, and for the evaluation of quantum dots and low-dimensional structures.