Effect of surface passivation process for AlGaN/GaN HEMT heterostructures using phenol functionalized-porphyrin based organic molecules

Abstract

In this work, we investigate an unexplored possibility of passivating the charged surface states on AlGaN/GaN high electron mobility transistor (HEMT) heterostructures by using organic molecules. This has further led to remarkable enhancement in the electrical properties of rectifying metal-semiconductor contacts on AlGaN/GaN. Phenol functionalized Zinc metallated-Tetra Phenyl Porphyrin (Zn-TPPOH) organic molecules were adsorbed on AlGaN/GaN via the solution phase to form a molecular layer (MoL). The presence of the MoL was confirmed using X-ray Photoelectron Spectroscopy (XPS). The thickness of the MoL was assessed as ∼1 nm, using Spectroscopic Ellipsometry and cross-sectional Transmission Electron Microscopy. XPS peak-shift analyses together with Kelvin Probe Force Microscopy revealed that the molecular surface modification reduced the surface potential of AlGaN by approximately 250 meV. Consequently, the Barrier height (ideality factor) of Ni Schottky diodes on AlGaN/GaN was increased (reduced) significantly from 0.91 ± 0.05 eV (2.5 ± 0.31) for Ni/AlGaN/GaN to 1.37 ± 0.03 eV (1.4 ± 0.29) for Ni/Zn-TPPOH/AlGaN/GaN. In addition, a noteworthy decrement in the reverse current from 2.6 ± 1.93 μA to 0.31 ± 0.19 nA at −5 V (∼10 000 times) was observed from Current-Voltage (I-V) measurements. This surface-modification process can be fruitful for improving the performance of AlGaN/GaN HEMTs, mitigating the adverse effects of surface states and polarization in these materials.

Surface Modification of AlN Using Organic Molecular Layer for Improved Deep UV Photodetector Performance

“…To investigate the presence of ZnTPP(OH) molecules on the AlN surface, XPS (PHI 5000 VersaProbe II) was used. and N in TPP (green color) were obtained at nearly 396.00 18,20,21 and 396.61 eV, 18,20,22 respectively. Deconvoluted Al 2p peaks are shown in Figure 5(c).…”

“…Deconvoluted Al 2p peaks are shown in Figure 5(c). An Al−N peak (blue color) was obtained at 73.13 eV, 18,21,23,24 and Al−OH, corresponding to native hydroxide (green color), was obtained at 74.25 eV. 18,20 Lastly, Figure 5(d) depicts deconvoluted O 1s spectra consisting of three peaks.…”

“…16 It has been reported that ZnTPP(OH) forms a SAM on the surface of semiconductors like Si, 17 GaN, 16 and AlGaN. 18 In this work, we have used ZnTPP(OH) for passivation of the electronic surface states of AlN by adopting a wet process. The reported method is advantageous for being simple, inexpensive, and easily repeatable.…”

Organic passivation of Al0.5Ga0.5N epilayers using self-assembled monolayer of Zn(II) porphyrin for improved solar-blind photodetector performance

“…A high CA of 98° was observed for SAM passivated film, which assured the presence of a hydrophobic layer on the Al0.5Ga0.5N surface. 29 31 Al−OH at 74.01 eV (FIG. 2 (e)), 27,34 HO−Ga at 530.66 eV, 31…”

Temperature dependent electrical studies on Cu/AlGaN/GaN Schottky barrier diodes with its microstructural characterization

“…Group III-Nitride based AlGaN/GaN high electron mobility transistors (HEMTs) are one of the most promising candidates for high-power and high-frequency microelectronic device fabrication owing to their superior material properties [1][2][3][4][5]. They possess a large band gap, high breakdown fields, high peak and saturation electron drift velocities, and high sheet charge densities on the order of 10 13 cm -2 at the interface [6][7][8].…”