Fabrication of Al/Gd2O3/P-Si/Al diodes and evaluation of electrical parameters under irradiation

The present study focused on the crystal structure, morphology, dielectric and electrical properties of n-type gadolinium oxide (Gd2O3) on p-type Czochralski-grown monocrystalline (CZ) silicon (100) wafers (CZ-pSi) as well as on glass, and determination of gamma rays' effects on Gd2O3/(CZ-pSi) diodes. The growth of the Gd2O3 layers was carried out by pulsed laser deposition technique (PLD) using altered laser energies (500, 600, 700, 800 and 900 mJ). Several Gd2O3/(CZ-pSi) diode samples were fabricated at room temperature and pressure (3.3 x10-2 Pa). The front and rear Al metal contacts were added to finalize Al/Gd2O3/(CZ-pSi)/Al devices. The surface morphology of the Gd2O3 layers was determined by AFM imagining. Surface roughness root mean square (RMS) calculations revealed that spherical shaped particles ~20-30 nm in diameter are present on the surface. The pulse laser energy has enormous effect on the grow of Gd2O3 layers, their particle sizes, deposition rates and surface morphology. Therefore, the membrane thickness decreases with increasing applied laser power to the target formed on the silicon wafer. UV-Vis studies displayed that the band structure for Gd2O3 layers on glass with substantial absorption at 290 nm has been formed the largest bandgap 3.46 eV for Gd2O3 film deposited at 800 mJ laser energy. Current-Voltage (I-V) measurements of the as-synthesized Al/Gd2O3/(CZ-pSi)/Al diodes were carried out for different laser power before irradiation. Other than a tiny increase in the semi-logarithmic representation at the beginning of the curves all curves indicate similar and typical leakage current behavior through oxides. All curves have a steeper rise above a certain voltage suggesting a change in the predominant charge transport mechanism. The capacitance-voltage (C-V) measurements of Gd2O3 films with different laser energies show similar behavior in frequency-dependent measurements. The capacitance values of Al/Gd2O3/(CZ-pSi)/Al diodes declined until -3V (totally depleted voltage). According to the findings the junction capacitance is inversely proportional to the reverse biased and directly proportional to the active voltages of Al/Gd2O3/(CZ-pSi)/Al diodes. Electrical property changes were evaluated under the influence of gamma ray radiation doses (3, 6, 12, 18, 24, 30, 36, 42 and 50 Gy) using Co-60 as the gamma ray source for Gd2O3/(CZ-pSi) deposited in 500 mJ laser energy at the frequency of 100 kHz. In the I-V curves, it was revealed that the current started to decrease with increasing radiation doses and continued to decrease in the direction of approaching zero with increasing radiation doses. In C-V curves, it turned out that there is a continuous shift in curves to the right of the pre-radiation curves which remains and increases with increase of radiation doses. The magnitudes of oxides capacitance shift up as the doses varies from 0 to 50 Gy. A specific sensitivity value was determined to be 44.8 ± 2.9 mV/Gy for 50 Gy dose.