Work

Structural and optical analysis of GaN and InxGa1-xN photodetectors fabricated by PEALD on silicon

Year: 2025

Type: article

Abstract: • GaN and InGaN thin films were deposited on Si substrates by PE-ALD and ALA methods. • The lattice mismatch is lower for the InGaN heterostructure as compared to GaN. • High photodetection and responsivity were observed for InGaN thin films. • InGaN exhibited a high photo-response and lower potential barrier than GaN. • InGaN had a better stability at high frequencies and lower trap density than GaN. The optical, structural, morphological and chemical properties of Gallium nitride (GaN) and Indium Gallium nitride (In x Ga 1-x N) thin films grown on Si (100) by plasma-assisted atomic layer deposition (PEALD) technique at a temperature of 300°C. X-ray diffraction (XRD) was performed, obtaining polycrystalline films with hexagonal phase to corroborate the obtaining of the materials. In addition, Atomic Force Microscopy (AFM) analysis showed surface roughness, R rms and R a values of 2.4 and 1.97 nm for GaN, and 5 and 1.8 nm for In x Ga 1-x N, respectively. Ultraviolet-visible (UV–Vis) spectroscopic analysis revealed that the band gap energy is 3.44 eV for GaN and 3.15 eV for In x Ga 1-x N. Both materials were compositionally analyzed by Secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS), obtaining a homogeneous distribution of the elements Ga, In, and N, but indicating the formation of indium and nitrogen oxides. Finally, as photodetectors, the GaN/Si and In x Ga 1-x N/Si devices were evaluated with their photoresponse showing a high response to visible light, good stability and low fall/rise times (GaN: τ Rise = 0.06 s, τ Fall = 0.35 s In x Ga 1-x N: τ Rise = 0.2 s, τ Fall = 0.22 s). The peak responsivity was observed at 350 nm for GaN and at 400 nm for In x Ga 1-x N, indicating a redshift in the spectral response caused by higher indium content in the ternary alloy.These devices were fabricated using uniform nanometric films on silicon, aiming for Complementary Metal-Oxide-Semiconductor (CMOS) compatibility.

Source: Results in Engineering