Communications in Physics

2024-01-09T15:49:37+07:00

Thermal behavior of irradiation-induced-deep level in bulk GaN used for fabricating blue light emitting diodes

2024-04-23T22:48:56+07:00

Bulk GaN was irradiated by 2 MeV electron beam at a fluence of 5 × 10¹⁶ cm² and studied by deep level transient spectroscopy (DLTS)_. After irradiation, a broad peak, including at least two traps, was detected. The trap D1 (E_C – 0.16 eV) observed from a broad peak is induced during the annealing process below 550K and completely annealed out at 550K after ~ 10 hours. The annealing process at 550K also forms a new trap D2 (E_C – 0.25 eV). From the isothermal study the activation energy of the trap D2 in the annihilation process is obtained and has a value of 1.3 ± 0.3 eV. The pre-factor of the annihilation process suggested this process to be related to the free-carrier capture by multi-phonon emission. From the thermal behavior, the trap D2 was suggested to be related to gallium vacancy.

Development of broadband ultraviolet pulsed laser using Ce:LiCAF crystal to determine SO\(_2\) gas concentration by differential absorption spectroscopy

2024-04-23T22:48:59+07:00

Earth’s atmosphere is a mixture of many gases which include pollutants such as SO₂, NO₂, NO, and O₃ that have absorption in the ultraviolet (UV) wavelength region. Therefore, the development of broadband UV laser sources that are useful in a differential absorption spectroscopy (DOAS) system for environmental research is necessary. In this research, we present the DOAS system using the Ce:LiCAF laser for determining SO₂ gas concentration in the atmosphere. The Ce:LiCAF laser has a full width at half maximum of 2 nm with a wavelength range from 286 to 291 nm and a peak wavelength of 288.5 nm. The results show that the DOAS system accurately determines the gas concentration with a measurement error of 6 %. This result can serve as the basis for developing practical DOAS systems with the ability to monitor a wide range of gasses and survey many other types of pollutants.